Search and rescue teams are scouring the rubble at these sites in hopes of finding survivors but didn't yet have a number for how many have died.
Kentucky Gov. Andy Beshear says he fears tornadoes have killed 70 people in the state and the death toll may exceed 100.
SEE ALSO | At least 50 people are likely dead following tornadoes in Kentucky, governor says
Here's what we know about the damage at the factory, warehouse and nursing home and the hunt for survivors:
Mayfield candle factory
One of the most devastated sites is the southwestern Kentucky city of Mayfield, where a tornado hit a candle factory while people were working. About 110 people were inside, Beshear said.
He said crews rescued about 40 people so far.
"We're going to lose a lot of lives," Beshear said.
Video from Mayfield showed what remained of the factory: a massive debris field, largely of twisted metal, several feet high, with rescuers using hands and machines to dig through.
Among the survivors was Kyanna Parsons-Perez, who said workers had been hustled to a safety area before the storm hit. While attendance was being taken, she saw "a little dust of wind."
"My ears start popping. And it was like the building, we all just rocked back and forth, and then boom -- everything fell on us," Kyanna Parsons-Perez told CNN.
Pinned by debris with others, she used her phone to broadcast on Facebook Live, and called 911, her mother and a coworker's relative. She knew rescuers were around only when she could feel pressure from above -- people walking on the debris.
"I was screaming like, 'Sir, can you please just get this so I can move my leg?' He said, 'Ma'am, there's about 5 feet worth of debris on top of you.'"
Rescuers eventually pulled her and others out, she said.
Ivy Williams was at the scene Saturday, looking for his wife of 30-plus years, who he says was at the factory.
"I hope she's somewhere safe," Williams said, through tears. "Please call me ... I'm looking for you, baby."
First responders have pulled "many, many" people out of the rubble, some alive and some apparently dead, storm chaser Michael Gordon told CNN Saturday morning from the scene.
"It's kind of hard to talk about. ... They're digging in that rubble by hand right now," Gordon said.
People were working there, as the factory has been "going 24/7" in part to meet Christmastime candle demand, US Rep. James Comer, who represents the area, told CNN.
Edwardsville Amazon warehouse
At least two people are dead after severe weather brought down the roof of an Amazon warehouse Friday night downstate near St. Louis, police said.
Officials said others were injured after the roof caved in at the facility near Edwardsville, Illinois. It's believed a tornado was to blame.
Police said it's still unknown how many people were in the building at the time of the collapse and how many people remain. The families of those inside the facility have said they are desperate for answers.
"We're just worried sick," said Sarah Biermann, whose husband works at the Amazon facility.
It is not immediately clear how many people were hurt, but officials said one person was flown by helicopter to a hospital. Dozens of people were able to escape without serious injury, Police Chief Mike Fillback said.
Rescue crews are still sorting through the rubble to determine if anyone was trapped inside, officials said. First responders are moving slowly to avoid injuries from hanging debris.
"We're deeply saddened by the news that members of our Amazon family passed away as a result of the storm in Edwardsville, IL. Our thoughts and prayers are with the victims, their loved ones, and everyone impacted by the storm. We also want to thank all the first responders for their ongoing efforts on the scene. We're continuing to provide support to our employees and partners in the area." Kelly Nantel, an Amazon spokesperson, said in a statement.
Monette Manor nursing home
First responders at the scene of a nursing home damaged by severe weather in Monette, Arkansas, where several people were trapped inside, Dec. 11, 2021. (KAIT)
A tornado struck the Monette Manor nursing home in northeastern Arkansas on Friday night, killing one person and trapping 20 people inside as the building collapsed, Craighead County Judge Marvin Day said.
Five people had serious injuries, and a few others had minor ones, he said. The nursing home has 86 beds.
CNN Wire contributed to this report.