Up to 100 people have been killed in a devastating series of tornadoes that ripped through Kentucky and several other US states, Kentucky Governor Andy Beshear says.
Mr Beshear said the string of tornadoes was the most destructive in the state's history.
"The level of devastation is unlike anything that I have ever seen," Mr Beshear said.
US National Weather Service said 36 separate tornadoes struck the Midwest of the country.
In Kentucky, they caused damage in more than a dozen counties.
The primary tornado travelled more than 320 kilometres across the state, Mr Beshear told an early morning news conference.
"The reports are really heartbreaking," Mr Beshear said.
"This has been one of the toughest nights in Kentucky history and some areas have been hit in ways that is hard to put into words.
More than 56,000 Kentuckians were without power, he said, adding he had declared a state of emergency and was deploying dozens of national guardsmen to communities.
The hardest-hit area appeared to be the city of Mayfield in Grave county, where a roof collapse at a candle factory caused "mass casualties".
Kyanna Parsons-Perez, who was inside the factory, said the roof collapsed soon after the workers could hear and feel the hollowing winds and the lights began flickering.
"We could feel the wind … then we did a little rock," Ms Parsons-Perez told NBC.
About 110 people were inside the factory when the tornado ripped through, the New York Times reported.
"We believe we'll lose at least dozens of those individuals," Mr Beshear said.
President Joe Biden ordered federal resources to be surged to locations with the greatest need.
In Tennessee, the severe weather killed at least three people, authorities said, while at least one person was killed and five were injured when a tornado shredded the roof of a nursing home in Monette in northern Arkansas.
Craighead County Judge Marvin Day said it was lucky more people weren't killed when the 90-bed facility was hit in Monette, a small community near the border with Missouri.
"It just took a direct hit from the tornado," Mr Day said.
"We were very blessed that more people weren't killed or injured in that. It could have been a whole lot worse."
Two factory workers killed
In Illinois, authorities said at least two workers died after the roof collapsed at an Amazon warehouse near St Louis late on Friday as tornadoes and strong storms blew through the area.
The death toll may continue to rise with several people not accounted for at the facility.
Amazon CEO Andy Jassy said the company was "heartbroken over the loss" of its staff members in Edwardsville and would continue to work closely with the local authorities on the rescue efforts.
The storms caused a CSX company freight train to derail in western Kentucky, although no injuries were reported, the Times said.
Bill Bunting, operations chief at the Storm Prediction Center, part of the National Weather Service, said at least five states were hit by the tornadoes: Illinois, Kentucky, Tennessee, Missouri, and Arkansas, the Times reported.
ABC/Reuters
