Severe thunderstorms are raking and flooding parts of the central US on Tuesday, including in Oklahoma, where a tornado appeared to touch down near the Tulsa International Airport in the early morning.
At least 21 tornadoes were reported in parts of Texas, Oklahoma, Missouri and Arkansas from early Monday to Tuesday morning, the National Weather Service said -- and more are possible, especially in parts of Missouri and Arkansas.
No severe damage was immediately reported near the Tulsa airport, where a tornado was reported shortly after 6:30 a.m. CT Tuesday. But radar indicated that a tornado was sending debris into the air, CNN meteorologist Chad Myers said.
"That debris was ... very close and moving toward" the airport, Myers said.
Severe weather is possible Tuesday in the central Plains, Missouri, Illinois, Arkansas, and parts of Texas and Louisiana.
Damaging winds and hail appear to be the main threats, but more tornadoes are possible, especially in southern Missouri and northern Arkansas.
Water rescues in Oklahoma
Storms on Monday and Tuesday were causing serious flooding in parts of Oklahoma -- and more flooding is expected to develop in states to the east.
Flash flood emergencies were declared Monday night and Tuesday morning in the Tulsa area, where more than 6 inches of rain have fallen in some locations this week.
The National Weather Service in Tulsa urged people in those areas to move to higher ground as more heavy rainfall is expected.
"We're seeing reports of flooding and water rescues across (northeast) Oklahoma," state emergency management spokeswoman Keli Cain told CNN Tuesday morning.
Multiple Oklahoma highways are closed due to high water or storm debris. Authorities warned drivers to stay off roads in anticipation of additional flooding expected overnight.
Roads in Ponca City, in northern Oklahoma, have turned into rivers, with the local government urging drivers to stay away from the water.
The county emergency manager reported flooding in the city had begun to enter buildings, CNN affiliate KTUL reported. Several roads had also been closed off.
In Mangum, near the state's border with Texas, city officials said a tornado hit a house and ripped the roof off a two-story apartment building, according to CNN affiliate KOCO.
The police department asked residents to "not get out and drive around."
"On top of emergency crews trying to fix power lines and other damage from the tornado," the department said, "the roads are now flooding due to the intense rain."
"By trying to check out the weather you are only putting yourself and the crews in further danger."
Stillwater Public Schools, in northern Oklahoma, announced schools in the district will be closed Tuesday "due to excessive flooding."
More flooding to come in the Plains and the Midwest
Because storms have repeatedly hit the same areas recently, a serious flooding threat has developed in the Plains and the Midwest.
About 17 million people were under flood or flash flood watches early Tuesday, including in Oklahoma City and Tulsa; Wichita, Kansas; and Kansas City and St. Louis, Missouri.
Serious river flooding -- including along the already swollen Mississippi River -- also is expected in the central US as another 2 to 5 inches of rain are expected to fall over the region in the next few days.