The death toll from storms and tornadoes in seven southern states in the US has risen up to 300, according to officials.
In the deadliest series of tornadoes in nearly four decades in the United States, 131 people were killed in Alabama, the worst-hit state which suffered "massive destruction of property," Governor Robert Bentley said on Thursday.
"We expect that number to rise," he said. He added that six million people were still without power.
The clusters of powerful tornadoes - more than 160 in total - combined with storms to cut a swathe of destruction heading from west to east over several days.
In preliminary estimates, other state officials reported 32 killed in Mississippi, 30 in Tennessee, 11 in Arkansas, 14 in Georgia, eight in Virginia and two in Louisiana.
Some of the worst devastation occurred on Wednesday in Alabama, where a massive 1.6 km tornado slammed into the town of Tuscaloosa, town of around 95,000 in the west-central part, killing at least 37 people including some students.
"It sounded like a chainsaw. You could hear the debris hitting things. All I have left is a few clothes and tools that were too heavy for the storm to pick up. It doesn't seem real," Steve Niven, a local resident, told the Reuters news agency.
"I can buy new things but you cannot replace the people. I feel sorry for those who lost loved ones."
Shops, shopping malls, drug stores, gas stations and dry cleaners were all flattened in one section of Tuscaloosa.
Wednesday was the deadliest day of tornadoes in the United States since 310 people lost their lives on April 3, 1974, weather forecasters said.
Tornadoes are a regular feature of life in the US South and Midwest, but they are rarely so devastating.
Al Jazeera's John Terrett, reporting from Birmingham, Alabama, said that electricity and water had been cut off and the city was a scene of devastation.
State of emergency
President Barack Obama has declared a state of emergency for Alabama and ordered federal aid for the stricken state.
"While we may not know the extent of the damage for days, we will continue to monitor these severe storms across the country and stand ready to continue to help the people of Alabama and all citizens affected by these storms," Obama said in a statement on Wednesday night.
Speaking to Al Jazeera, Adrienne Veilleux, Accuweather meterologist, said: "Severe weather season in the United States does generally run from April until June so it's not unusual to see strong thunderstorms.
"However, the number of thunderstorm reports with hail, the damaging winds and even tornadoes, is a bit unusual."
Floods were a big concern throughout the storm-hit area, where rain compounded with melted snow to cause rising rivers and saturated soils.
Several states suffered power outages as well as property and infrastructure damage that could prove costly to repair.
The storms forced the Tennessee Valley Authority to close three nuclear power plants in Alabama and knocked out 11 high voltage power lines.
"Teams have pre-deployed to begin debris removal and search and rescue operations as soon as conditions permit," said Lauree Ashcom, a spokeswoman for the Alabama Emergency Management Agency.
Governors in Alabama, Arkansas and Tennessee have declared a state of emergency, while in Mississippi, Haley Barbour, the state governor, declared a state of emergency for 39 counties.
Residents in Tennessee are coping with flooding, power outages and blocked roads. Flooding became more widespread in Arkansas on Wednesday after several days of intense storms.
Violent weather has pummeled much of the US South this month. Two weeks ago, at least 47 people died as storms tore a wide path from Oklahoma to North Carolina.
"This year has been quite bad already. We have already seen over 700 reports just within the month of April, and this is actually record breaking," Veilleux added.
"The threat for tornadoes tonight is actually winding down, we are still going to see some severe weather in through the night time hours.
"And another threat of severe weather is going to be moving in, late into the weekend, however, the threat for tornadoes is not going to be quite as widespread as we have seen with this event."