Emergency officials were preparing to survey tornado damage Saturday morning following the second major fatal storm to strike the Oklahoma City metropolitan area in several days.

The storm toppled cars and left commuters trapped on an interstate highway as it bore down during Friday's evening rush. Law enforcement officers and Red Cross damage assessment workers planned to head after dawn to areas in the city and its suburbs hit by what the National Weather Service reported were "several" tornadoes that rolled in from the prairie.

Five people were reported killed, including a mother and baby found in a vehicle. Amy Elliott, a spokeswoman for the state medical examiner, said early Saturday that she had no immediate word of additional fatalities. About 50 people were hurt, five critically, hospital officials said.

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An overturned semitrailer rests on its side on the eastbound lanes of Interstate 40, just east of El Reno, Okla., after a reported tornado touched down Friday. (Chris Machian/Omaha World-Herald/Associated Press)

Meteorologists who had warned about particularly nasty weather said the storm's fury didn't match that of a deadly twister that struck suburban Moore last week. Violent weather also moved through the St. Louis area, ripping the roof off a suburban casino.

Violent weather also moved through the St. Louis area, ripping part of the roof off a suburban casino.

Friday's broad storm hit during the evening rush hour and stuck around, causing havoc on Interstate 40, a major artery connecting suburbs east and west of the city, and dropping so much rain on the area that streets were flooded to a depth of 1.2 metres.

To the south, a severe storm with winds approaching 130 km/h rolled into Moore, where a top-of-the-scale EF5 tornado killed 24 on May 20.

Rick Smith, the warning coordination meteorologist for the National Weather Service at Norman, said in a text message relayed by the Storm Prediction Center that Friday's storm was "not even close" to causing the type of destruction like the one that hit Moore.

The U.S. averages more than 1,200 tornadoes a year and most are relatively small. Of the 60 EF5 tornadoes to hit since 1950, Oklahoma and Alabama have been hit the most — seven times each.

Heavy rain and hail hampered rescue efforts in Oklahoma City. Frequent lightning roiled the skies well after the main threat had moved east. Highways and streets were clogged late into the night as motorists worked their way around flooded portions of the city.

Oklahoma Highway Patrol Trooper Betsy Randolph said troopers found the bodies of a woman and an infant near their vehicle. Randolph said it's not known if the woman was driving into the storm when it hit around 7 p.m. local time (8 p.m. ET) Friday.

Emergency officials reported that numerous injuries occurred in the area along I-40, and Randolph said there were toppled and wrecked cars littering the area. Troopers requested a number of ambulances at I-40 near Yukon, west of Oklahoma City.

"We're scrambling around," said Lara O'Leary, a spokeswoman for the local ambulance agency. "There is very low visibility with the heavy rain…so we're having trouble getting around.

Standing water was several feet deep, and in some places it looked more like a hurricane had passed through than a tornado.

In Missouri, gamblers rushed from the floor of the Hollywood Casino in the St. Louis suburb of Maryland Heights as a storm ripped off its roof. Trees and power lines were also down, and more than 40,000 people lost power.

In Oklahoma, storm chasers with cameras in their cars transmitted video showing a number of funnels dropping from the supercell thunderstorm as it passed south of El Reno and into Oklahoma City just south of downtown. Police urged motorists to leave I-40 and seek a safe place.

Residents seek shelter

"I'm in a car running from the tornado," said Amy Sharp, who last week pulled her fourth-grade daughter from the Plaza Towers Elementary School as a storm approached with 210 mph winds. "I'm in Norman and it just hit Yukon where I was staying" since last week's storm.

"I'm with my children who wanted their mother out of that town," Sharp said, her voice quivering with emotion.

At Will Rogers World Airport southwest of Oklahoma City, passengers were directed into underground tunnels and flights were canceled. However, people near the area said they weren't aware of any damage.

'I normally don’t get afraid but I have to admit I actually feel fear. There's only so much the human spirit can take.'—Moore resident Allyson Reneau

Television cameras showed debris falling from the sky west of Oklahoma City and power transformers being knocked out by high winds across a wider area.

As the storm bore down on suburban Oklahoma City, Adrian Lillard, 28, of The Village, went to the basement of her mother's office building with a friend, her nieces, nephews and two dogs.

"My brother's house was in Moore, so it makes you take more immediate action," Lillard said while her young nieces played on a blanket on the floor of the parking garage. "We brought toys and snacks to try our best to keep them comfortable."

Well before Oklahoma's first thunderstorms fired up at late afternoon, the Storm Prediction Center in Norman was already forecasting a violent evening. From the Texas border to near Joplin, Mo., residents were told to keep an eye to the sky and an ear out for sirens.

Jennifer McNatt of the U.S. National Weather Service told CBC News that many people around Oklahoma City were seeking shelter ahead of the approaching storm.

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Parts of Oklahoma City experience extreme flooding after multiple tornadoes passed through the area Friday. (Nick Oxford/Associated Press)

"The people of Oklahoma have been prepared for this event," McNatt said, referring to several days of tornadoes throughout the state over the last week and a half.

Allyson Reneau, a resident of Moore, Okla., said she was moving her family ahead of the storm's arrival.

"I normally don’t get afraid but I have to admit I actually feel fear," Reneau told CBC News Friday evening as she headed for an underground shelter. "There's only so much the human spirit can take."

Friday evening's weather came after flash flooding and tornadoes killed three people in Arkansas late Thursday and early Friday. Three others were missing in floods that followed 15 centimetres of rain in the rugged Ouachita Mountains near Y City, 200 km west of Little Rock.

This spring's tornado season got a late start, with unusually cool weather keeping funnel clouds at bay until mid-May. The season usually starts in March and then ramps up for the next couple of months.

With files from CBC News