(CNN) -- A storm system that wrought havoc on the Oklahoma City metropolitan area, generating a handful of tornadoes that killed a mother and a child and sent tens of thousands scrambling for shelter, moved late Friday toward Missouri.
The National Weather Service warned a "confirmed and extremely dangerous tornado" was near the city of Harvester, about 25 miles northwest of St. Louis. The tornado was moving east at 50 mph, said Colene McEntee, the St. Charles County Emergency Management coordinator.
As authorities in Missouri urged people to take shelter, officials in Oklahoma were working to determine how many people had been killed and injured in the storm that battered the state's largest city.
A mother and a child were killed as a result of severe weather, and another 14 were injured, said Brooke Cayot of Integris Canadian Valley Hospital in suburban Yukon. Of those being treated at the hospital, three were in critical condition, she said.
At the height of the storm, the National Weather Service issued a tornado emergency for a number of areas in and around Oklahoma's capital city, with tornadoes reported outside Moore, near the suburb of Bethany, north of Union City and outside Tinker Air Force Base.
Parts of Interstates 35 and 40, which cut through Oklahoma City and Moore, were "a parking lot," the weather service said, warning that those caught in the heavy rush hour traffic "are in danger."
"We've got a nightmare situation going on right now," Betsy Randolph, a state Highway Patrol spokeswoman, told CNN.
"They are essentially sitting ducks on the interstate."
Overturned big rigs and cars littered portions of the roadway, and thousands more were believed to be stuck in the traffic.
"My biggest concern right now is the traffic that is out on the highway right now," Oklahoma Gov. Mary Fallin said.
She said she has called out the National Guard, the Oklahoma Highway Patrol and the state Office of Emergency Management to "try to get the traffic moving" and get people to shelter.
The weather service issued the tornado emergency for Oklahoma City as well as its suburbs of Moore, Yukon and Bethany.
Oklahoma City's Will Rogers World Airport was evacuated over the threat from the approaching tornado, and travelers were sheltered in the airport's basement at the height of the storm, authorities said.
"They are now in the process of slowly allowing people out of their shelter. They are bringing employees up now, and then the passengers will be able to come up once the terminal is properly staffed," said Karen Carney, a spokeswoman for the airport.
"Right now, the airport has no power. Without power, they probably will not be able to allow passengers into the secure areas of the airport. But they obviously can't allow any takeoffs and landings without power, either."
Even those in the National Weather Center -- a building on the University of Oklahoma campus with tenants that include the National Severe Storms Laboratory and NOAA's Storm Prediction Center -- "have been urged to stay away from windows due to potential for 80-90 mph winds," according to a tweet from weather service's Norman office, which also is based in the building.
Police and firefighters were responding to reports of damage in El Reno, just outside Union City, but it was not immediately known how bad the damage was, Mayor Matt White said.
Authorities were urging people in the path of the tornado to take immediate cover, and Fallin was urging residents not to take any risks.
In Moore, where a massive tornado leveled much of the city this month, Mayor Glenn Lewis said it was unimaginable that the city was in the path of another tornado.
A reported tornado moved four miles northwest of Moore, according to the National Weather Service forecasters and storm spotters.
The storm was so fierce that the Weather Channel's Mike Bettes, known for his on-the-ground severe weather reports, said his Tornado Hunt vehicle was thrown about 200 yards.
"Airbags deployed. All are safe," Bettes said in a post on Twitter.
More than 50,000 customers were without power by early Friday evening in the Oklahoma City area because of severe weather, the Oklahoma Gas and Electric Co. said.
More than half the city of Mustang, 17 miles south of Oklahoma City, was without power, Mustang Fire Chief Roy Widmann said.
CNN's Joe Sutton, Jennifer Feldman, Chandler Friedman and Dave Alsup contributed to this report.