Many people were trapped after a roof partially collapsed at an Amazon.com Inc warehouse near St. Louis late on Friday, after tornadoes and strong storms blew through the area, local authorities said.
The Collinsville Emergency Management Agency said it was a "mass casualty incident", adding that multiple people were trapped inside the warehouse in Edwardsville, southern Illinois.
In a posting on Facebook, the agency did not give details, and there was no word yet of how many people had been injured or killed.
Emergency service vehicles surrounded the scene.
An Amazon spokesperson said the company was assessing the situation and damage at the facility.
One woman outside, Sarah Bierman, said she was very worried about her husband, who works at the warehouse.
"I talked to him about eight o'clock tonight, a little before I texted him, and he was returning to the warehouse to drop his van off," she told a reporter.
"And I haven't heard from him since, I just heard through the news and we live in Edwardsville; we lost power. So I decided to come down here to see what was going on, and I had no idea the building looked that bad. And I'm just; I'm worried sick."
"My prayers are with the people of Edwardsville tonight, and I've reached out to the mayor to provide any needed state resources," Illinois Governor JB Pritzker tweeted.
The US National Weather Service had issued tornado warnings on Friday night for areas in several states including Arkansas, Tennessee, Missouri and Illinois.


Russian drone, missile attack on Kyiv hits residential buildings
US, Iran talks conclude in Doha, focused on Strait of Hormuz
Trump honours Theodore Roosevelt in North Dakota, debuts new Air Force One
Kenyan court charges 8 schoolgirls with fellow students' murder
At least 5 people killed in fire in Antwerp apartment block
Three people die in Mexico World Cup celebrations as fans crowd streets
After Venezuela quakes, citizens lead rescues amid military theft accusations
Two dead after wildfire guts house in northern Greece
