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Rescuers search through the wreckage of the Mayfield candle factory
A desperate search for survivors is under way in parts of six US states devastated by powerful tornadoes that have left at least 83 people dead.
Dozens more people are missing and entire towns were destroyed by about 30 tornadoes on Friday.
President Biden has declared a disaster in Kentucky, the worst-affected state.
More than 70 people have died in the state, including dozens in a candle factory, and the death toll is expected to rise above 100.
Local congressman James Comer, working with rescuers in the ruined town of Mayfield, said the tornado there was the widest ever seen.
“It’s the most devastating storm damage I’ve seen in my entire life. We’ve had tornadoes that have been the same length as this tornado but we’ve never had one with the width of this tornado,” he said.
Forty people have been rescued from the collapsed candle factory in Mayfield but 60 more remain missing and Kentucky Governor Andy Beshear, who has visited the scene, said it was unlikely there were more survivors.
“There’s at least 15ft of metal with cars on top of it, barrels of corrosive chemicals that are there. It’ll be a miracle if anybody else is found alive in it,” he said.
One candle factory employee made a desperate plea for help on Facebook from under the wreckage as co-workers could be heard moaning in the background.
“We are trapped, please, y’all, get us some help,” said Kyanna Parsons-Perez – who was later rescued – in the broadcast played on CNN.
Mayfield resident Tony Meeker described the moment the tornado hit.
“Out of nowhere the sirens went off and then not long after that our ears popped. I mean it was like the pressure dropped. And then it felt like our house was about to just be gone, get carried off,” he said.
“It looks like a bomb went off. I don’t know how anybody could’ve lived. I feel bad for anybody that didn’t make it or people who got stuck. I’m sure it was terrifying.”
Mr Beshear said the tornado had wrecked places all along its 227-mile (365km) path, including the town of Dawson Springs.
“One block from my grandparents’ house, there’s no house standing and we don’t know where all those people are,” he said.
Tornadoes also collapsed an Amazon warehouse in Edwardsville, Illinois, killing six people. Police said it was still unknown how many workers were missing. Amazon founder Jeff Bezos said he was “heartbroken” and pledged support to the community.
Mr Biden has signed a Federal Emergency Disaster Declaration, releasing funds for Kentucky. He said the loss of life caused by the tornadoes was a “tragedy”.
The president said teams from the emergency agency Fema would go to Kentucky on Sunday to offer additional resources including help with temporary housing for those whose homes had been destroyed or badly damaged.
Tens of thousands of people in the state remain without power and water.
Emergency funds were also available for the other affected states – Missouri, Arkansas, Illinois, Tennessee and Mississippi – if they needed it, Mr Biden said.
By Nomia Iqbal, BBC News, Bowling Green, Kentucky
The destruction is extraordinary to see. The strong line of storms tore through a neighbourhood in Bowling Green in southern Kentucky
Dozens of homes are severely damaged or completely destroyed. Power lines hang loosely on the roads and whole trees have been uprooted. Toys, books, clothing are scattered across peoples’ lawns.
In one home, half of the roof collapsed into the garage, burying the owner’s car. A man approaches the battered front door with his children and peers inside. His 97-year-old aunt lives inside, he says, and he cannot get hold of her.
“We’re worried. She doesn’t have a cell phone or anything,” he says. “God, I’m hoping she got out safe”. A few minutes later after speaking to a relative on the phone, relief spreads across his face. “She was in the bath tub but got out safely. She’s fine. She’s fine.”
Further down the street a nearby petrol station has been decimated, and one solitary pump station stands in the forecourt. A huge air conditioning unit that would usually sit on top of the kiosk has come entirely off the roof and blown over to the other side of the road.
As the sun sets over the town, it is eerily quiet. The only noise and light come from the nearby police cars patrolling the area.
Other incidents in Kentucky included a train derailment during extreme winds in Hopkins County. One train car was blown 75m up a hill and another landed on a house. No one was hurt.
Local officials also described how two children were reported missing during a tornado but were then found alive in a bathtub that had been pulled outside by the force of the wind.
Three people were killed in Tennessee, local officials said without giving further details. Two people were killed in Arkansas, one of them in a nursing home after it partly collapsed. One death was confirmed in Missouri.
The longest a tornado has travelled along the ground in the US was a 219-mile storm in Missouri in 1925 that claimed 695 lives.