Two people died and more than 80 were hurt when at least 140 vehicles collided on a Texas highway in dense fog.
The carnage left lorries twisted on top of each other and authorities rushing to pull survivors from the wreckage.
"It is catastrophic," said Jefferson County Sheriff's Office deputy Rod Carroll. "I've got cars on top of cars."
He said 80 to 90 people were taken to hospital, with 10 to 12 of those in serious to critical condition. He said 140 to 150 vehicles were involved in the pile-up.
The Thanksgiving holiday morning crash happened on Interstate 10 about 80 miles east of Houston.
Deputy Carroll said the fog was so thick that officers did not immediately realise they were dealing with multiple accidents.
The Texas Department of Public Safety said a crash on the eastbound side of the highway led to other accidents in a dangerous chain reaction. There were multiple crashes on the other side of the highway as well.
DPS trooper Stephanie Davis said two people were killed in an SUV crushed by a tractor trailer. She said at least 100 cars and trucks were involved in the accident.
I-10's eastbound lanes were re-opened last night after more than eight hours.
Deputy Carroll said uninjured drivers tried to help as authorities sorted through the wreckage.
"It's just people helping people," he 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."