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Massive tornadoes tore a town-flattening streak across the South, killing at least 269 people in six states and forcing rescuers to carry some survivors out on makeshift stretchers of splintered debris. Two of Alabama's major cities were among the places devastated by the deadliest twister outbreak in nearly 40 years.

As day broke Thursday, people in hard-hit areas surveyed obliterated homes and debris-strewn streets. Some told of deadly winds whipping through within seconds of weather alerts broadcast during the storms Wednesday afternoon and evening.

"It happened so fast it was unbelievable," said Jerry Stewart, a 63-year-old retired firefighter who was picking through the remains of his son's wrecked home in Pleasant Grove, a suburb of Birmingham. "They said the storm was in Tuscaloosa and it would be here in 15 minutes. And before I knew it, it was here."

He and his wife, along with their daughter and two grandchildren, survived by hiding under their front porch. Friends down the street who did the same weren't so lucky — Stewart said he pulled out the bodies of two neighbors whose home was ripped off its foundation.

Alabama officials confirmed 180 deaths, while there were 33 in Mississippi, 33 in Tennessee, 14 in Georgia, eight in Virginia and one in Kentucky.

President Barack Obama said he would visit Alabama Friday to view damage and meet with the governor and families devastated by the storms. Obama has already expressed condolences by phone to Gov. Robert Bentley and approved his request for emergency federal assistance.

The National Weather Service's Storm Prediction Center in Norman, Okla., said it received 137 tornado reports into Wednesday night. The storms forced authorities in some places into makeshift command posts after their headquarters lost power or were damaged, and an Alabama nuclear plant was using backup generators to cool units that were shut down.

A tornado expert at the Oklahoma center said it appears some of the tornadoes were as wide as a mile and likely packed a wallop that only 1 in 100 twisters ever reach. It could be days, however, before scientists make an official determination.

Some of the worst damage was in Tuscaloosa, a city of more than 83,000 that is home to the University of Alabama. Neighborhoods there were leveled by a massive tornado that barreled through late Wednesday afternoon and was caught on video by a tower-mounted news camera.

"When I looked back, I just saw trees and stuff coming by," said Mike Whitt, a resident at DCH Regional Medical Center who ran from the hospital's parking deck when the wind started swirling and he heard a roar.

On Thursday morning, he walked through the neighborhood next to the hospital, home to a mix of students and townspeople, looking at dozens of homes without roofs. Household items were scattered on the ground — a drum, running shoes, insulation, towels, and a shampoo bottle. Streets were impassable, the pavement strewn with trees, pieces of houses and cars with their windows blown out.

Dr. David Hinton was working at the hospital when the tornado hit. He and his wife had to walk several blocks to get to their house, which was destroyed. Several houses down, he helped pull three students from the rubble. One was dead and two were badly injured. He and others used pieces of debris as makeshift stretchers to carry them to an ambulance.

"We just did the best we could to get them out and get them stabilized and get them to help," he said. "I don't know what happened to them."

Back from an aerial tour Thursday morning, Tuscaloosa Mayor Walter Maddox said the tornado tore a streak of "utter destruction" through the city. There were at least 36 people dead in the city's police jurisdiction, and searches continue for the missing.

"We have neighborhoods that have been basically removed from the map," he said.

Because the city's emergency management building was destroyed, authorities are using Bryant-Denny Stadium at the University of Alabama as a command post.

University officials said there didn't appear to be significant damage on campus, but the school canceled final exams and postponed commencement from May until August. Dozens of students and locals were staying at a 125-bed shelter in the campus recreation center.

The storm system spread destruction from Texas to New York, where dozens of roads were flooded or washed out. The governors of Alabama, Mississippi and Georgia issued emergency declarations for parts of their states.

The National Weather Service said the deaths were the most since a tornado outbreak killed 315 people in 1974.

A research meteorologist at the Oklahoma prediction center, Dr. Harold Brooks, said the average tornado is on the ground for a couple of miles, measures a couple hundred yards wide and packs top winds of 100 mph. He said most reasonably built structures can withstand storms like those, but the ones that hit Wednesday appeared much stronger.

"There's a pretty good chance some of these were a mile wide, on the ground for tens of miles and had winds speeds over 200 mph. Well, that's obviously a bigger problem," he said.

Brooks said there is some evidence that a single tornado could have started at the Mississippi-Alabama state line before plowing through Birmingham and Tuscaloosa and into Georgia. If that's the case it could be among the longest-tracking tornadoes in history.

In Alabama, where as many as a million people were without power, Bentley said 2,000 national guard troops had been activated and were helping to search devastated areas for people still missing. He said the National Weather Service and forecasters did a good job of alerting people, but there is only so much that can be done to deal with powerful tornadoes a mile wide.

The storm also forced the Browns Ferry nuclear power plant about 30 miles west of Huntsville to shut down its three units because of damage to the utility's transmission lines, the Tennessee Valley Authority said. Diesel generators were being used to cool the reactors. The safety systems operated as needed and the emergency event was classified as the lowest of four levels, the Nuclear Regulatory Commission said.

In Smithville in northeastern Mississippi, the police station, post office, city hall, an industrial park with several furniture manufacturing facilities and a grocery store were among dozens of buildings ripped apart. A church was cut in half, and pieces of tin were wrapped high around the legs of a blue water tower.

Jessica Monaghan, 24, walked through the wreckage with her 9-month-old son, Slade Scott, strapped to her back, and the baby's father, 23-year-old Tyler Scott, by her side.

Their house was still standing, though the home belonging to Tyler Scott's mother was flattened. He was at work — he's a firefighter in nearby Tupelo — and Monaghan was at home watching TV when broadcasters warned the town could be hit within 10 minutes. By then, she said, the storm was there.

"The baby was already in the closet. I grabbed the cat and got in the closet, too," Monaghan said. "You could just feel the pressure. It really was like a freight train."

In Georgia, parts of Trenton were heavily damaged. Lisa Rice, owner of a tanning salon there, survived a tornado by climbing into a tanning bed with her two daughters, 19-year-old Stormy and 21-year-old Sky.

She said they were working in the salon about 6 p.m. when her husband called to report a tornado warning. She saw the dark sky outside and some debris flying.

"I'd already told the girls which bed we were going to climb into if we need to. So, we got in it and closed it on top of us," Rice said. "Sky said, 'we're going to die.' But, I said, no, just pray."

She said they could hear the cracking of the roof coming off, and the feel the air rushing over. The 30-second ordeal left the salon in ruins, but the family was happy to be safe.

"We're still alive," she said. "We have a lot to be thankful for."

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Reeves reported from Tuscaloosa. Associated Press Writers Michelle Williams in Trenton, Ga., Holbrook Mohr in Smithville, Miss.; Anna McFall and John Zenor in Montgomery; Meg Kinnard in Colombia, S.C.; Bill Fuller and Alan Sayre in New Orleans; Dorie Turner in Atlanta; and Bill Poovey in Chattanooga, Tenn., contributed to this report.