At least 23 people have been killed as tornadoes struck Lee County in eastern Alabama, authorities say.
County Sheriff Jay Jones said there had been “catastrophic” damage and there were fears more bodies would be found. The number of injured is not yet known.
Rescue efforts have been halted until dawn due to the danger of searching in the dark.
The most devastating tornado struck the area around Beauregard, carving a path at least half a mile (0.8km) wide.
The National Weather Service (NWS) classified it as at least an EF-3 – meaning winds of up to 165mph (266km/h).
It warned people to “stay out of damaged areas so first responders could do their job”.
Where have the tornadoes struck?
The area around Beauregard, about 60 miles (95km) east of Alabama’s state capital, Montgomery, appears to have borne the brunt. The tornado there struck at about 14:00 (20:00 GMT) on Sunday.
Footage showed snapped poles, roads littered with debris and houses without roofs.
Sheriff Jones said some homes had been reduced to slabs.
Authorities fear the death toll could rise.
Residents of Smiths Station told local TV they had seen businesses destroyed there. A large bar called the Buck Wild Saloon had had its roof torn off.
Sheriff Jones said: “The challenge is the sheer volume of the debris where all the homes were located. It’s the most I’ve seen that I can recall.”
Tornado warnings were also issued for Georgia, Florida and South Carolina. Footage showed smashed buildings and snapped trees in Talbotton, about 80 miles south of Atlanta.
Tornadoes were also reported in Walton County and Cairo in northern Florida.
