The city was stunned by the devastation that not only hit homes and commercial areas, but also destroyed much of the city's public works infrastructure -- including the city's emergency management administration headquarters.
"We are critically short of men, material and equipment," Mayor Walter Maddox said at a news conference today.
The mayor asked people to stay off the streets and conserve water, and for gawkers to stay away. He said "sightseers" are only getting in the way of emergency crews.
"This is going to be a very, very long process" of cleaning up and rebuilding, he said. "During this time we ask for patience and we ask for prayers."
About 2,000 Alabama National guard soldiers have been activated to help with search and rescue.
"There is some massive devastation out there," Gov. Bentley said. "We have some people that are hurting."
Two nuclear power plants in Browns Ferry, Ala., had to be shut down after the storm damaged its transmission system. Emergency generators kicked in to cool down the reactors safely.
In Ringgold, Ga., near the Tennessee border, officials shut down major roads leading into the city because of what Catoosa County Sheriff Phil Summers said was "downed power lines, broken gas lines and looting."
"There are lots of spectators and we are not allowing access inside of Ringgold at this time," the sheriff said.
Summers said he saw the tornado in the air just before it touched down.
"It was something that I've never seen before except on TV. And like they say, there's a moment of silence and then you see the devastation," he said.
The sheriff said the tornado was in Ringgold for about five minutes and it continued into Tennessee. Five people died and police are looking for others whose homes were so badly damaged that "only foundations are left," Summer said.
Christopher England at the University of Alabama ran up to the roof of his building to videotape a devastating tornado as it hit Tuscaloosa.
"We just saw this massive huge mile wide tornado and we didn't know where it was going. We didn't know if it was coming towards us or away from us or what," he said.
One of the victims was an off-duty police officer in northern Mississippi who died while shielding his daughter from a falling tree on a camping trip. She wasn't hurt.
ABC News Radio, Michael S. James, Mike Marusarz, Jessica Hopper and the Associated Press contributed to this report.