A powerful storm system that delivered dozens of tornado sightings across the Southern Plains spawned a confirmed twister Tuesday morning near Tulsa International Airport, as highways across Oklahoma remained closed due to floodwaters.

The National Weather Service's Tulsa Office said the confirmed tornado was reported around 6:37 a.m. near the airport and moving northeast at 50 mph.

"Take shelter now!" the NWS office warned on Twitter.

The tornado in Tulsa didn't damage the airport, but passengers were moved into shelters for about 30 minutes, spokesman Andrew Pierini told the Associated Press. Many flights were canceled or delayed because of the storms. bout a dozen homes near the airport were damaged by the twister, according to Tulsa Area Emergency Management spokeswoman Kim MacLeod

"We had to rescue a man, he was pinned under a tree this morning," MacLeod told the AP. The man's condition was not immediately known and damage assessments were still ongoing.

The tornado near Tulsa was part of a powerful system bringing the threat of severe weather expected to continue throughout the day as storms move east.

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"Severe storms have continued overnight across the Plains, and today the threat shifts eastward to eastern portions of the Plains and the Mississippi River Valley," Fox News Senior Meteorologist Janice Dean said Tuesday "Large hail, damaging winds, flooding, and more tornadoes are possible through tonight."

Storms Monday evening flipped campers at Lucas Oil Speedway in Hickory County, Missouri, injuring seven people, four of whom were taken to hospitals. The speedway's grandstand also was destroyed, forcing cancellation of racing this weekend that was expected to draw about 3,000 campers. Details about injuries were not immediately available.

Besides the severe weather, the storms brought a deluge of rain, causing the Oklahoma Department of Transportation to shut down Interstate 40 in El Reno, about 25 miles west of Oklahoma City, because of high water Tuesday morning. The National Weather Service said up to five inches of rain had fallen since Monday.

"This water is very, very dangerous," Fox News' Aishah Hasnie said on "FOX & Friends" from Oklahoma City. "A dangerous situation for much of the city here as there continues a flash flood warning. Also, power has been out in many areas across the city, and there could be downed power lines in that water as well."

Multiple road closures were reported in El Reno, Choctaw and Del City, with water rescues also ongoing.

In El Reno, city officials opened a temporary shelter and closed schools after 7 inches of rain fell in just a few hours, FOX25 reported.

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In Stillwater, home to Oklahoma State University, emergency responders were rescuing people from their homes after the area was besieged by high water.

The Storm Prediction Center had warned of an unusually high risk for severe weather Monday for parts of Oklahoma and Texas. Damage was reported in many areas Monday night, including the town of Mangum, but no deaths have been reported.

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Glynadee Edwards, the Greer County emergency management director, told the Associated Press that some homes in Mangum incurred roof damage and the high school's agriculture barn was destroyed, but the livestock survived.

"The pigs are walking around wondering what happened to their house," she said.

The Associated Press contributed to this report.