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Tornadoes roared across the Plains on Wednesday, causing at least a dozen injuries, damage to homes and flash flooding in Oklahoma.

At least 20 twisters were sighted across three states — with multiple tornadoes reported in Kansas, Oklahoma and Nebraska, according to Nick Wiltgen, a senior meteorologist with The Weather Channel.

Oklahoma Gov. Mary Fallin was preparing an emergency declaration and was planning to tour hard hit areas on Thursday, Oklahoma Department of Emergency Management spokeswoman Keli Cain told NBC News.

Officials said at least 12 people were injured — two critically — when a tornado tore through two mobile home parks on the south side of Oklahoma City.

"Crews are searching the areas now, going door-to-door looking for victims in need of assistance," Oklahoma City Police Department Capt. Dee Patty said.

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The Oklahoma Department of Emergency Management opened its operation center due to the severe weather conditions, reporting statewide power outages, damaged homes and road closures due to flooding.

A flash flood emergency was declared in Oklahoma City for the first time in history, city officials said in a post on Twitter, as much of central Oklahoma was hit with heavy rain and flash flood warnings.

"Deadly and dangerous. Do not drive," officials said in the tweet.

I got a time lapse video of the Norman supercell/tornado from the 6th floor of the NWC. Stay safe! #okwx pic.twitter.com/Y2BZ7zwb2q — Andrew Dzambo (@AndrewDzambo) May 6, 2015

“Seek higher ground now!” the National Weather Service said in an alert. “This is a potentially life-threatening situation!” Five to eight inches of rain had fallen in affected areas as of Wednesday night, the NWS said, with another four to five inches of possible rainfall to come.

The wild weather knocked out power to more than 28,000 people across Oklahoma, according to reports from local power companies, while the Will Rogers World Airport in Oklahoma City was evacuated twice on as severe storms approached the area.

Just before 10 p.m. CT, the Grady County Sheriff’s Office warned that a tiger safari in Tuttle had been damaged by severe weather and live animals from the facility were on the loose.

NBC affiliate KFOR later reported that all the animals in the facility were accounted for.

Kansas was also hard-hit, with a series of tornado sightings and large hail pummeling parts of the state. No major damage was reported.

In Nebraska, 10 to 15 homes were damaged near Grand Island, and between Hardy and Ruskin, near the Kansas line, according to The Associated Press.

Short video from the tornado earlier today in Lincoln Co, KS #kswx pic.twitter.com/yAqav7C6Gr — Matt Unruh (@UnruhMatt) May 6, 2015

The National Weather Service also issued tornado watches for parts of west central and northwest Texas, until at least 9 p.m. CT.