Two people died and up to 100 were hurt when at least 100 vehicles collided on a Texas highway in dense fog.
The Thanksgiving holiday morning crash left trucks twisted on top of each other and authorities rushing to pull survivors from the wreckage.
Twelve of those injured were in a critical condition, officials said.
The pile-up happened on the on Interstate 10 about 80 miles (128km) east of Houston.
"It is catastrophic," said Jefferson County Sheriff's Office Deputy Rod Carroll. "I've got cars on top of cars."
It wasn't immediately clear how the pile-up began, but Mr Carroll said the fog was so thick that officers didn't immediately realise they were dealing with multiple accidents.
I-10's eastbound lanes were expected to remain closed for most of Thursday.
Texas Department of Public Safety trooper Stephanie Davis told KFDM that two people in an SUV died after the crash. She said at least 100 cars and trucks were involved in the accident.
Mr Carroll said uninjured drivers tried to help as authorities sorted through the wreckage.
"It's just people helping people," Mr Carroll said. "The foremost thing in this holiday season is how other travellers were helping us when we were overwhelmed, sitting and holding, putting pressure on people that were injured."