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NBC News – by Erin McClam

A monster tornado ripped through southern Oklahoma City and the suburb of Moore on Monday afternoon, leaving homes and schools in ruins and fires burning out of control.

There was no immediate word on casualties, but aerial footage showed major destruction: homes in rubble, cars flipped over and crushed, residents milling around in shock or combing through debris.

“A large part of the community has been affected,” Jayme Shelton, a spokesman for Moore, told MSNBC.

A forecaster for NBC station KFOR said the tornado was kicking up a debris cloud about 2 miles wide as it tracked east into residential neighborhoods in the Moore area.

Forecasters said the twister could be an EF5, the most devastating category of storm with sustained wind speeds topping 200 mph and “incredible” damage. The National Weather Service will confirm the storm’s intensity.

Oklahoma City police told NBC News southern portions of the city as well as the Moore suburb sustained “major damage… a lot of damage.”

Two elementary schools were heavily damaged, possibly completely destroyed, KFOR reported. Those schools are Briarwood Elementary in Oklahoma City and Plaza Towers Elementary in Moore.

Other Oklahoma towns were in the twister’s path as it headed toward Meeker, Okla., KFOR reported.

Watch live video of storms from KFOR TV

Tens of millions of people from Texas to the Great Lakes were warned to brace for severe weather one day after a tornado outbreak killed two elderly men in Oklahoma and turned a trailer park into splinters.

The gravest threat appeared to be in Oklahoma and parts of Missouri, but forecasters warned that strong storms, damaging wind and pounding hail were possible as far north as Minnesota and Wisconsin.

In all, an area covering 55 million people was under risk of severe weather, the National Weather Service said.

On Sunday, twisters killed two men in Shawnee, Okla., ages 79 and 76, and injured 21 others. The state medical examiner confirmed the second death Monday morning.

The storms also destroyed mobile homes, flipped trucks and sent people across 100 miles running for cover. In Kansas, a weather forecaster was forced off the airas a tornado bore down on his station.

“You can see where there’s absolutely nothing, then there are places where you have mobile home frames on top of each other, debris piled up,” Mike Booth, the sheriff of Pottawatomie County, Okla., told The Associated Press. “It looks like there’s been heavy equipment in there on a demolition tour.”

The weather service office in Norman even posted a Twitter alert warning of a tornado about to strike one town:

Oklahoma Gov. Mary Fallin declared a state of emergency for 16 counties. In Edmond, Randy Grau said he looked out a window and saw what he thought was a flock of birds heading down the street.

“Then I realized it was swirling debris,” he told The Weather Channel. “That’s when we shut the door of the safe room.”

In Wichita, Kan., a tornado touched down near the airport. Two tornadoes touched down Sunday night outside Des Moines, Iowa.

The storm system is making a slow march east. Severe storms will threaten the same part of the country Tuesday and parts of the Northeast on Wednesday, the weather service said.

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