Residents emerged yesterday to view the full scope of the devastation left by powerful tornadoes that tore through small towns in south-central United States, killing at least 18 people.
More big twisters were expected as violent thunder and hail storms moved through a large part of the southern United States, from Texas to Tennessee, forecasters said.
Tornadoes struck the region on Sunday, flipping cars, ripping up homes and uprooting trees.
One of the towns hardest hit by the storms, Vilonia, Arkansas, intensified its search for survivors yesterday, after the arrival of daylight allowed a good look at the storm damage.
Vilonia's police chief, Brad McNew, told US television that tornado damage had rendered his town unrecognisable. "It's houses completely down to the foundations," McNew told NBC television.
Rescuers had worked through the night using searchlights as they sifted through mountains of rubble searching for survivors.
The Arkansas Department of Emergency Management said 15 people were killed when tornadoes touched down on Sunday, while an official with the Oklahoma Emergency Management Agency said there were at least two tornado victims in the state.
Local media reported another fatality in the state of Iowa.
McNew said there was not yet a final tally of casualties in his town of just 4,000 people.
He said, however, the toll would surely have been far worse, if not for sirens that warned citizens of the twister.
"The storm warnings went out fairly early," he said. "I went to a tornado shelter myself with my family which was a couple miles away from where we were at. A lot of people in the community were there.
"If you see the destruction that is here, even though we've lost some lives, there's many lives that was saved because of the storm warnings," McNew said.
Officials said Vilonia was struck three years ago by a tornado. But yesterday's twister was "a lot worse than it was three years ago," McNew said.
Twisters also devastated large sections of the town of Mayflower just northwest of the Arkansas state capital Little Rock.
The National Weather Service warned of the threat of "a severe weather outbreak" beginning late yesterday, affecting several states, including the lower Mississippi Valley, Tennessee Vally and Central Gulf Coast states.
Watch: Midwest tornadoes leave devastation in their wake
"Numerous tornadoes are expected, some of which could be intense, the NWS said.
US President Barack Obama offered condolences and promised federal government aid.
Television footage showed trucks crushed like empty cans in Arkansas, homes ripped in half, and entire residential blocks reduced to rubble.
Some homes were uprooted from their foundation. In Iowa, the tornado also dumped heavy rain, snapped trees and lifted the roof off a medical centre in the town of Oskaloosa.
Dozens of homes were reported destroyed in nearby Kansas, although officials so far have reported no fatalities there.