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SAN FRANCISCO (Reuters) - Does Twitter have a credibility problem?

For many, a single fake tweet from the Associated Press account that briefly roiled financial markets on Tuesday, driving the Dow Jones industrial average down about 145 points, vividly reaffirmed the fearsome, near-instantaneous power of the 140-character message.

But the security lapse also revived doubts about Twitter's place in the media landscape - and its ultimate value - at a moment when its status as one of today's essential information networks had seemed all but cemented.

Just a week after social media networks took criticism for helping circulate misinformation about the alleged perpetrators of the Boston Marathon bombing, Twitter's security shortcomings fell under a harsh spotlight Tuesday after a hacker group commandeered the AP Twitter account and falsely reported that explosions in the White House had injured President Barack Obama.

The AP was only the latest hacking victim in recent days after Twitter accounts belonging to National Public Radio, CBS 60 Minutes and others were breached. Last year, Reuters News was the victim of hackers who briefly took over one of its Twitter accounts and posted false tweets.

The latest hack was by far the most significant: the single AP tweet stunned investors and effectively wiped out $136.5 billion of the S&P 500 index's value in a matter of minutes.

Although the news agency later disclosed that one of its employees may have inadvertently given away company passwords as the result of a "phishing" attack by the hackers, security experts quickly faulted Twitter for its longstanding failure to implement two-factor authentication, a double-layered password feature used by the likes of Google Inc and Microsoft Inc that might have prevented the spate of high-profile Twitter hijackings.

"It's one of those cases that we are seeing too often. It's getting unnerving," said Robert Quigley, a journalism lecturer specializing in social media at the University of Texas. "What media organizations need to do is pressure Twitter to have a more secure website."

Twitter declined to comment for this article.

The company has also repeatedly declined to discuss its product roadmap, although it has signaled that it will soon unveil two-factor authentication, including a public job posting in February that suggested it was hiring to tackle the problem.

Mark Risher, the founder of a security consultancy that counts social media companies Pinterest and Tumblr among its clients, said introducing more measures like two-factor authentication would make Twitter more cumbersome to use and potentially slow its user growth - a critical concern for a company that relies on advertising revenues. But he warned that a prolonged rash of high-profile hacks, and an eroding sense of user trust, would hurt Twitter more.

"There's always a tradeoff between convenience and safety," Risher said. "But a security issue damages Twitter's brand."

NEWSWIRE OR PLATFORM

For Twitter, the hacking has raised questions about its credibility just as it is beginning to assume a central role in a fast-changing media landscape, with the volume of tweets rising to more than 400 million a day. Earlier this month, the Securities and Exchange Commission ruled that U.S. companies may report material information such as quarterly results on Twitter, as long as investors are alerted in advance. Days later, Bloomberg L.P. said it would funnel Twitter directly into its terminals used by thousands of traders on Wall Street.

At the same time, the world's leading news organizations and Twitter, which has 200 million users around the world, have become increasingly intertwined in a symbiotic, if sometimes troublesome, relationship.

Dan Gillmor, a journalism professor at Arizona State University, said the hacks have especially hurt news outlets because their Twitter accounts are often the primary way that their news reaches consumers who may not subscribe to a newspaper or have access to a newswire.

Twitter has touted itself as a critical newswire of sorts, such as during the 2011 tsunami in Japan, when it helped emergency responders locate survivors, or when it became a vital lifeline for some New Yorkers as television sets fell dark during Hurricane Sandy last year.

But last week, in the wake of the Boston bombings, some of those who previously viewed Twitter as an indispensable news source began turning against the service upon discovering that the wisdom of crowds is, in fact, an adage not often applicable on the Internet.

Steve Brunetto, a senior executive at Edgewave, a network security company, said Tuesday's hacking undermined Twitter at a sensitive time.

"On the heels of the Boston Marathon bombing, everyone's trying to figure out, 'Okay, where does Twitter fit into that news cycle? Where does Twitter fit into disseminating information?'" Brunetto said. "They've got an opportunity to legitimize themselves as a real player in that information life cycle but they get knocked down a peg every time somebody says, 'Oh, you can't believe what you read on Twitter.'"

Jeff Jarvis, a prominent Internet pundit and a journalism professor at City University of New York, said that the confusion caused by social media in recent weeks was not an indictment of social media but rather a reminder that the onus falls on professional reporters to verify information.

"No, the Internet's not broken," Jarvis said.

BAR-ROOM DEBATES

The rise of social media means that "you now hear more bar-room debates and speculation than before," he added. "But that doesn't mean you should believe it more than you ever did."

Tom Schrader, managing director for U.S. equity trading at Stifel Nicolaus Capital Markets in Baltimore, said there were a lot of clues in the false AP tweet that should have kept traders from reacting, in particular the wording of the message.

"We saw it, we saw the initial reaction. Initially our reaction was, pull your bids (until we) see whether this is legit or not. We found no legitimacy to it and went back into the market as normal," he said.

Oli Freeling-Wilkinson is chief executive officer of Knowsis, a London company that picks out and amalgamates financially relevant tweets and other social media content for traders. "We do have spam controls in place, but it's an ongoing war," he said. "It's much more difficult to work out what's going on when people are hacking into official accounts, especially in the heat of the moment."

While Twitter has occasionally signaled that it believes it could become more than a passive distribution network - a shift marked by last year's purchase of Summify, a small startup that specialized in surfacing relevant news - it has also taken pains to distance itself from the content of tweets and maintain strict neutrality from a legal perspective.

Twitter Chief Executive Dick Costolo told an Online News Association gathering last autumn that Twitter's primary responsibility was to create a platform, rather than to play an editorial role in determining which tweets people should see.

"A company trying to build media is creating or curating content, and that's not the kind of company we're creating," Costolo said.

Gillmor, from Arizona State, said Twitter did not need to guarantee the quality or veracity of its content in order to grow into a media juggernaut.

"It's not whether Twitter is credible or not, it's what people do with it," he said. "Every news organization feels it has no alternative but to use Twitter. But everyone at the traditional news organizations has to be thinking really hard about what that means, from whether the security is sufficient on these third-party platforms to what it means to be turning part of your stuff over to new kinds of publishers."

(Reporting By Gerry Shih; Additional reporting by Jennifer Saba, Ryan Vlastelica and Caroline Valetkevitch in New York and Alina Selyukh in Washington; Editing by Claudia Parsons)

PARIS (Reuters) - Sanofi reported lower-than-expected first-quarter earnings on Thursday as the effects of last year's patent losses and foreign exchange headwinds crimped growth from diabetes drugs, vaccines and rare disease unit Genzyme.

But the French drugmaker said it expected to return to growth in the second half of the year and confirmed that annual profit would be flat to 5 percent lower than in 2012 at constant exchange rates.

"We are in the last quarter of the patent cliff ... The numbers, when you look at them, really reflect the history, but I think it's the future of the company that is particularly exciting," Chief Executive Chris Viehbacher told reporters.

Sanofi's closely watched business net income, which excludes items such as amortization and legal costs, dropped 33 percent to 1.61 billion euros ($2.1 billion) on sales of 8.06 billion, down 5.3 percent.

Sales were hit by generic competition, austerity measures in Europe and the depreciation of several currencies, including the dollar and the Japanese yen, against the euro.

Sanofi had been expected to post quarterly business net income of 1.75 billion on sales of 8.3 billion, according to a Thomson Reuters poll.

In February Sanofi disappointed investors' hopes it would return to growth at the beginning of this year.

The expiry of Sanofi's patent on anti-blood clotting drug Plavix, once the world's second-best selling prescription drug, is expected to slice around 800 million euros off earnings in the first half of 2013, Sanofi said.

Drugmakers across the world have been struggling with patent expiries as well as cutbacks in healthcare spending by cash-strapped European governments.

Pfizer Inc reported much lower-than-expected first-quarter sales on Tuesday, hurt by weak demand for its Prevnar 13 vaccine used to prevent pneumonia and other infections, and it trimmed its 2013 profit forecast.

Merck & Co Inc reported a surprising drop in quarterly sales of diabetes medicine Januvia, its biggest product and a frequent driver of quarterly earnings, and the drugmaker cut its full-year profit forecast on Wednesday.

EMERGING MARKETS

Sales in emerging markets, one of Sanofi's priorities to drive growth along with diabetes and rare disease treatments, reached 2.72 billion, an increase of 6.5 percent, and accounted for 33.7 percent of group sales.

Sales of Aubagio, a multiple sclerosis pill that was approved in the U.S. last September and is part of Sanofi's ambition to become a major player in this therapeutic area, reached sales of 20 million in the first quarter.

Sanofi also said two new members will join its executive committee on July 1 following the retirement of Hanspeter Spek, Sanofi's head of global operations.

Peter Guenter will be head global commercial operations, while Pascale Witz will be in charge of global divisions and strategic commercial development.

Sanofi shares, which have gained around 11 percent this year, closed at 52.87 euros, giving it a market capitalization of 110.4 billion euros.

($1 = 0.7580 euros)

(Reporting by Elena Berton; Editing by Leila Abboud)

Fifth-place Palace will now go into their final game of the season against Peterborough on Saturday, knowing a point will almost guarantee a top-six finish and keep alive their Premier League ambitions.

Millwall would likely ensure their second-tier future with a draw at Derby County.

Josh Wright went close for Millwall, while Palace's Yannick Bolasie was denied by a good save from the hosts' keeper David Forde.

Crystal Palace (69 points), Bolton Wanderers (67), Nottingham Forest (67) and Leicester City (65) all enter the final weekend with a chance of finishing in the final two playoff spots.

Cardiff City have already been promoted to the Premier League as champions while Hull and Watford are fighting for the second automatic promotion spot. Brighton have already secured a playoff place.

Millwall, on 56 points, are involved in a fight to avoid the drop with Sheffield Wednesday (55), Peterborough (54), and Barnsley (54).

Wolverhampton Wanderers (51) retain only slim hopes of staying up and bottom club Bristol City are already relegated.(Reporting by Toby Davis; editing by Pritha Sarkar)

Tuesday night's clash erupted when members of the opposition coalition unfurled a banner in the National Assembly denouncing a ruling that strips them of most legislative powers unless they recognize the April 14 election victory of President Nicolas Maduro.

Assembly member Julio Borges appeared on an independent television station soon after Tuesday night's brawl with blood running down one side of his swollen face. The opposition said at least 17 of its allies and five pro-government deputies were injured.

Opposition lawmaker Ismael Garcia said government loyalists threw the first punches. Pro-government legislators appeared on state TV accusing opposition members of attacking them. Video showed groups of legislators shoving and pushing each other on the floor.

The opposition has refused to accept Maduro's narrow victory, saying the government's 1.49 percent margin resulted from fraud, including votes cast in the names of the thousands of dead people found on current voting rolls.

In retaliation, the government-dominated assembly has barred opposition lawmakers from public speaking and sitting on legislative committees.

Both sides planned to take to the streets of Caracas on Wednesday for marches celebrating International Workers' Day. Each appeared to be trying to avoid confrontation by choosing separate locations and calling for peaceful demonstrations, although fears of violence were running high.

Opposition candidate Henrique Capriles is boycotting an official audit of the election and plans to file a challenge seeking to overturn it in court.

On Tuesday, legislator Pedro Carreno, head of the governing United Socialist Party of Venezuela in the National Assembly, asked for an extension of the ban on public speaking by the opposition, whose members unfurled a banner reading "coup against the parliament."

"Without a word, like cowards, they came at us from behind," said Garcia, the opposition lawmaker.

Maduro accused the opposition of provoking the violence, which he condemned and called on the country to work out its disputes peacefully.

National Assembly chief Diosdado Cabello, considered one of the most powerful men in the country for his ties to the business community and army, has repeatedly defended barring opposition lawmakers from speaking. He said that if they don't recognize the legitimacy of the presidential election, they are casting doubt on the national electoral system that elected them, thus losing their own legitimacy.

The opposition lawmakers have also lost their seats on legislative commissions.

Carreno described government backers' action in the fight as self-defense.

"If I'm standing here and you come to attack me, it's likely that I'll react, but it's the aggressor who went out with a black eye," he said.

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Associated Press writer Michael Weissenstein contributed to this report.

For the last 10 years I have ignored my birthday and tried to avoid all celebrations. I'll take a vacation alone and have a great time. My family understands how I feel and gives me no grief.

I met Wade five years ago. He's a co-worker who has become a good friend. Wade has made it his goal in life to make me celebrate my birthday. I have tried being nice about the presents and even a surprise birthday party one year, but I really prefer to be left alone. I never told him my birth date. He had access to HR records and found out on his own.

He says I am "rude" for not letting him celebrate my birthday. Other than this issue, he's a great guy. Advice, Abby? -- NON-OBSERVANT IN FLORIDA

DEAR NON-OBSERVANT: Wade may be a "great guy," but he appears to be insensitive when it comes to respecting the feelings of others. Before your next birthday, "remind" him that you prefer not to celebrate or acknowledge it. A good friend should listen and respect the other person's wishes instead of trying to impose his or her will, and don't be shy about saying so.

DEAR ABBY: I am one of four sisters. Two of my sisters, their husbands and I want to plan a trip to Italy. We do not want to include our fourth sister and her husband. None of us like him or can forgive how he abused her in the past. For her sake, we tolerate him at family gatherings and holidays, but none of us want to be with him for an extended period. We also don't think his health would allow him to do a lot of the things we want to do on this vacation.

How do we plan this trip while excluding our sister and her husband without hurting her feelings or causing a big family blowup? Should we just not mention it? Or should we tell her she's invited but not her husband? Please advise. -- SIS IN A PICKLE

DEAR SIS: Secrets like this have a way of getting out. It might be a slip of the tongue by one of your sisters or their husbands, or some other relative who knows about the trip.

Surely your sister knows how you all feel about her husband, so it won't be a shock if you tell her she is invited but he is not. Under the circumstances I doubt if she will join you, and there will probably be hurt feelings. But sneaking this past her would be like trying to smuggle dawn past a rooster, and I don't think it would be long before she finds out anyway.

DEAR ABBY: My husband and I have been married for nine years. I worked until 2010, and then quit to be a stay-at-home mom to our two small children.

Because I no longer work, I watch what I spend, but my husband never lets me forget that he is the wage earner. When I want to spend money he always says, "What's in it for me?" or, "What do I get?" I feel like this degrades me. Why does he do this to me? -- STAY-AT-HOME MOM IN GEORGIA

DEAR STAY-AT-HOME MOM: Your husband may say it because he feels stressed or resentful that he is the sole wage earner now. The first time it happened you should have responded that "what's in it for him" is that his children have a full-time mother, which the majority of children today don't have, and "what he gets" out of it are offspring who have a mother rather than a caregiver raising them.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Write Dear Abby ator P.O. Box 69440, Los Angeles, CA 90069.

For everything you need to know about wedding planning, order "How to Have a Lovely Wedding." Send your name and mailing address, plus check or money order for $7 (U.S. funds) to: Dear Abby, Wedding Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Shipping and handling are included in the price.)

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The space tourism company Virgin Galactic appears to be go for its first rocket-powered test flight of SpaceShipTwo a commercial rocket ship for passenger space travel.

There is a palpable buzz of a possible test flight of on Monday (April 29) at the Mojave Air and Space Port in Mojave, Calif. The test is rumored to be a 20-second burn of SpaceShipTwo's novel hybrid rocket motor in flight.

SpaceShipTwo is designed to use the rocket motor to power private launches that will carry six passengers and two pilots to suborbital space and back. So the possible test flight would be a major milestone for the spacecraft and Virgin Galactic. []

Virgin Galactic's founder, the British billionaire Sir Richard Branson, hinted at a powered flight test on April 23 during an interview with the Las Vegas Sun newspaper at an event for his other company, Virgin Atlantic, which began Los Angeles to Las Vegas service last week.

"We're hoping to break the sound barrier. That's planned Monday," . "It will be a historic day."

Mum's the word, with fingers crossed

Despite Branson's tantalizing comments,and Mojave officials are tight-lipped on Monday's test, given the fact that technical or weather delays could affect their plans.

"Test flight schedules have to remain flexible to be responsive to weather and a host of other factors, so can't give you a specific date," said Virgin Galactic CEO and President George Whitesides. "But what is certain is that the team is getting close to first rocket-powered flight, which is an important milestone for the company and the program."

Whitesides told SPACE.com that whenever the first flight occurs, the primary goal "is smooth and safe demonstration of the vehicle system in terms of rocket ignition, shut off, and aerodynamic controls."

Officials in Mojave were also short on details for any SpaceShipTwo tests on Monday.

"While we can't comment on tenant test plans, we always strive to accommodate our friends in the press," Stuart Witt, CEO and general manager of the , told SPACE.com in response to a query.

"Flight Research Tests require three things: airspace allocation, vehicle in a ready state and acceptable weather," Witt said.

While a pilot hitting the start button on SpaceShipTwo's motor is not a hosted event for press and public, Witt added, "we try to accommodate the interest of the public. We never know times or dates it is the nature of flight test."

According to Mojave-based company Scaled Composites, which is building SpaceShipTwo and its WhiteKnightTwo carrier plane for Virgin Galactic, the piloted craft has undergone 25 glide flight tests since October 2010. Thewas a nitrous vent test and was labeled as powered flight number 1 "mission rehearsal."

Hybrid rocket motor 101

According to Virgin Galactic's website, SpaceShipTwo's hybrid motor stands apart from all-liquid and all-solid rocket engines.

"Here the fuel is in solid form and the oxidizer is a liquid. The passage of the oxidizer over the fuel is controlled by a valve which allows the motor to be throttled or shut down as required," the website explains.

Hybrid motors offer both simplicity and safety, Virgin Galactic officials added. According to the company description: "This is the type of motor that SpaceShipTwo will employ and that was used by SpaceShipOne. It means that the pilots will be able to shut down the SpaceShipTwo rocket motor at any time during its operation and glide safely back to the runway. The oxidizer is Nitrous Oxide and the fuel a rubber compound; both benign, stable as well as containing none of the toxins found in solid rocket motors."

Looking good for flight

SpaceShipTwo's hybrid motor supplier, the commercial spaceflight company Sierra Nevada Corporation (SNC), has performed over 300 hybrid rocket test firings. The company also developed the rocket engine for the first private spacecraft to reach space, SpaceShipOne, which won the $10 million Ansari X Prize in 2004.

Furthermore, Sierra Nevada is developing a similar hybrid engine to power its reusable , a spacecraft that is vying to provide astronaut flights for NASA.

As for the prospects of an upcoming SpaceShipTwo hybrid motor flight, Mark Sirangelo Corporate Vice President, SNCs Space Systems, told SPACE.com: "We are looking good for the flight. Motor passed all its multiple qualification burns and tests with no issue."

Leonard David has been reporting on the space industry for more than five decades. He is former director of research for the National Commission on Space and is co-author of Buzz Aldrin's new book "Mission to Mars My Vision for Space Exploration" out in May from National Geographic. Follow us on,and. Original article on.

Though many people have evacuated, many of us have houses built on stilts, designed for these situations, so a few of us have held out at home. It isn't always easy to bear the water as it comes up under the house, rising to a record 22.3 feet (normal levels for this time of year are about 12.6), yet it is still better to be at home, for some.

During a flood of this magnitude, the river takes what it will. Debris from yards and homes floats by, as well as full-sized trees. Loggers in the area left some huge logs sit, in this neighborhood, prior to the waters rising, which some are having to contend with as they float up around their houses.

At the time of this writing, the river level is receding, currently at 21.06 feet. Yet, in this immediate area, it is projected that the river will still cover the road for quite some time, likely at least two weeks. The whole story will not be visible until the waters have receded to something of a normal level.

The 24-year-old senior IT worker, whose name was not released, was arrested on Tuesday night at his Sydney office, the Australian Federal Police said. The man, who police say has claimed to be a high-level member of the hacking group, was charged with two counts of unauthorized modification of data to cause impairment, and one count of unauthorized access to, or modification of, restricted data. If convicted, he could face up to 12 years in jail.

Lulz Security, or LulzSec, is an offshoot of the hacking group Anonymous. LulzSec was formed in 2011 and quickly grabbed headlines after claiming responsibility for a series of high-profile cyberattacks against the CIA, Sony Pictures, the U.S. Public Broadcasting Service and Britain's Serious Organized Crime Agency.

Several members of the group have been arrested in recent years, including its reputed leader, known as Sabu. Sabu turned out to be FBI informant Hector Xavier Monsegur, who federal officials said helped them build a case against several other hackers. Two weeks ago, British LulzSec hacker Ryan Ackroyd pleaded guilty to several cyberattacks.

Australian Federal Police Superintendent Brad Marden said the man arrested on Tuesday hacked into an Australian government website and defaced it earlier this month. Marden would not say which website was attacked, but said it did not belong to a federal agency. Police don't believe any sensitive data stored on the site was accessed in the attack, and don't believe anyone else was involved in the hack.

The man, from Gosford about 80 kilometers (50 miles) north of Sydney claimed to be the Australian leader of LulzSec, Australian Federal Police Commander Glen McEwen said. But Anonymous Australia appeared to laugh off those claims on Twitter. In response to a follower asking if anyone knew who the man was, the group tweeted: "Nope not part of the usual suspects on any of our chans of communication."

Police began investigating the man two weeks ago after they discovered the government website had been hacked.

"This individual was operating from a position of trust who had access to sensitive information from clients including government agencies," McEwen said. "The AFP believes this man's skill sets and access to this type of information presented a considerable risk for Australian society."

The man was released on bail and ordered to appear in court next month.

The massive system was wreaking havoc from the Rockies to the Rust Belt, and officials were blaming two road deaths Thursday on the storm.

Up to a foot of snow was expected in parts of Minnesota and the Dakotas. Snow and ice closed highways in Colorado and Wyoming. Rivers surged beyond their banks from downpours in Missouri, Iowa and Illinois. Tornadoes caused scattered damage in Oklahoma. Hail caused a wreck that injured a high school teacher and her students. Lightning temporarily knocked out a nuclear power plant. Rain caused a sinkhole that devoured three cars in Chicago.

In the Plains and Midwest, seemingly every community was under some sort of watch or warning.

Alex Sosnowski, a meteorologist for AccuWeather, said the storm's biggest punch had come from its intense rainfall: "There's been a general 3 to 6 inch swath of rain from portions of Oklahoma all the way up to southern Wisconsin."

The system will thin out as it heads east but could still spell trouble in the Appalachian Mountain region Friday and in some spots along the East Coast by Friday night, Sosnowski said.

Midwesterners will be glad to see it go.

Minnesota State Police say 16-year-old Jonathon Pohlen of Houlton, Wis., was killed Thursday afternoon when he lost control on snowy Interstate 94 in eastern Minnesota, crossed over the median and collided with a truck's trailer.

Meanwhile, flash floods are being blamed for the death of an 80-year-old motorist south of St. Louis. Police in De Soto, Mo., said the woman's car was swept Thursday off Highway E into Joachim Creek. The woman was not immediately identified.

In Clarksville, Mo., a small, scenic Mississippi River town about 60 miles north of St. Louis, some 100 people were working feverishly to build a makeshift levee of gravel, plastic overlap and sandbags in a bid keep downtown dry. The heavy rain caused a sudden surge in the river, with a crest expected by early Sunday.

"I'm confident it will work, but I'm not confident we're going to get it done in time," Clarksville resident Richard Cottrell, 64, said of the sandbag levee. "It's a race against the clock."

City Clerk Jennifer Calvin said the Federal Emergency Management Agency was bringing in 500,000 additional sandbags, but the nearest available gravel had to be trucked in from nine miles away, and there weren't enough available trucks to expedite the effort.

The Mississippi is expected to crest 8 to 12 feet above flood stage at several spots in Iowa, Illinois and Missouri. The Missouri River was also expected to exceed flood stage by up to 10 feet at some Missouri locations.

Other rivers were rising quickly, too.

The town of Wyoming, Mich., evacuated about 25 homes in the path of the flooding Grand River. The Grand Rapids suburb called in all available police, firefighters and public works employees to help with sandbagging.

In suburban Chicago, Nick Ariano helped rescue a friend's grandmother, who became trapped in a home filling with water after a branch of the flooding DuPage River spilled over its levee.

Ariano, his friend and another man raced to a sporting goods store to buy inflatable rafts, then paddled out to the home and got Mille Andrzejewski, in her mid-80s, to safety. The three friends got some enjoyment out of the raft ride, despite the eeriness of floating over submerged cars and mailboxes.

"As kids growing up we used to raft down the river," Ariano said with a laugh.

About 60 miles southwest of Chicago, Morris Hospital in Grundy County began evacuating 44 patients to other hospitals after a nearby creek and the Illinois River rose and water crept into the basement, spokeswoman Janet Long said. Elective surgeries scheduled for Friday were canceled, although the emergency department remained open, the hospital said on its website.

In Gary, Ind., a flood-fighting drill scheduled for Friday was canceled because of real flooding. Sandbagging operations were under way along the Little Calumet River.

Flash flooding was common. In Utica, Ill., the fire department evacuated a mobile home park. In Marshall County, Ill., boats were needed to rescue trapped morning commuters.

In Ava, Mo., a school bus carrying several children stopped because of water on the road. The driver turned around to go back, only to find flooding behind him, too. The driver and kids waited at a nearby home until help arrived.

Perhaps the storm's most bizarre scene came in Chicago, where a massive sinkhole opened and swallowed two parked cars and one that was driving through. The driver was hospitalized but was expected to survive.

Flooding from all-night rain storms forced authorities to close sections of several major expressways around Chicago, canceled classes at some schools and scrapped around 550 flights at O'Hare International Airport.

The storm-swollen Chicago River was being allowed to flow into Lake Michigan, in part to relieve sewer backups. Meanwhile, workers were furiously filling sandbags and putting up barricades along the Chicago River's north branch. The river was diverted away from the lake more than a century ago to keep pollution out of the lake, the source of the city's drinking water.

Winds, possibly from a tornado, damaged dozens of homes in Spavinaw, Okla., injuring one person. Another twister damaged a few buildings near Paris, Mo. High winds also blew two tractor-trailers off a highway near Monroe City, Mo.

In Kansas, large hail was blamed for an accident that injured six high school students and their teacher. The Kansas Highway Patrol said the wreck happened Wednesday on Interstate 70 near Russell. The group was returning to school from an art exhibition when the teacher lost control of the SUV and struck a car.

The U.S. Nuclear Regulatory Commission said a lightning strike knocked out power to a northern Illinois nuclear plant for several hours Wednesday night, but emergency generators kicked in to keep the site running. Exelon Generation said reactors will remain offline until safety checks and procedures are completed.

Up to a foot of new snow was expected in northern Minnesota. Duluth has already received 24 inches of snow this month, and the additional snowfall could push it past the April record of 31.6 inches set in 1950

Snow and ice forced closure of sections of Interstate 70 and Interstate 25 in Colorado. The Wyoming Department of Transportation warned drivers to watch for black ice.

The snow didn't bother 63-year-old Bill Zubke, a retired motivational speaker who was relaxing in the lobby of a downtown Sioux Falls, S.D. Zubke, from Watertown, S.D, described the unpredictable weather as "just April in South Dakota," though temperatures ordinarily reach into the 60 this time of year.

"We're South Dakotans," he said. "We can handle it."

___

Keyser reported from Chicago. Associated Press writers Maria Sudekum in Kansas City, Mo., Dirk Lammers in Sioux Falls, S.D., and Tammy Webber in Chicago contributed to this report.

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Watch The Associated Press' video here: http://bit.ly/13rcncw