At least 22 people, some children, have been killed after tornadoes struck Lee County in eastern Alabama, authorities said.
Sheriff Jay Jones told the Associated Press the toll could rise, but rescue efforts had to stop until dawn due to the danger of searching in the dark.
It is unknown how many are injured. Authorities have blocked off the area.
The National Weather Service (NWS) classified the first tornado to strike as at least an EF-3 – meaning winds of up to 165 miles per hour (266km/h).
Who was hurt?
Authorities say they are still working to identify the victims and the injured.
Family members reportedly said one of the victims was an eight year old in the town of Beauregard.
“We’ve never had a mass fatality situation, that I can remember, like this in my lifetime,” Lee County coroner Bill Harris reportedly said.
Rescuers have yet to reach some areas, he said, and coroners from other parts of the state were coming to help.
East Alabama Medical Centre said it was treating more than 40 people injured by the extreme weather, and was expecting more.
What was the damage?
Sheriff Jones described the damage as “catastrophic”, saying one tornado cut a path of destruction quarter of a mile (0.4km) wide and several miles long.
PowerOutage.US says there are about 4,000 customers without power across Alabama, with about 2,000 of those in Lee County.
Cold weather is forecast for the region after the tornadoes, with temperatures predicted to drop to near freezing.
What’s been the reaction?
Alabama Governor Kay Ivey posted on Twitter to warn residents there could be more extreme weather to come.
“Our hearts go out to those who lost their lives in the storms that hit Lee County today,” she wrote.
President Donald Trump also tweeted, asking people to “Please be careful and safe”.
The National Weather Service said it would send three survey teams to assess the damage caused by tornados across the state on Monday.
Schools in the Lee County will be closed on Monday, authorities said, although this will not include school districts in Opelika and Auburn within the county.