A tractor-trailer plowed into 11 cars stopped on an interstate highway in coastal Mississippi early Saturday, killing four, injuring four, and closing the highway for more than six hours, police said.

The crash started when a pickup truck and the trailer it was hauling overturned, spilling used computer equipment across eastbound Interstate 10, about 10 miles from the Louisiana state line, said Lt. Johnny Poulos of the Mississippi Highway Patrol.

“That 18-wheeler continued eastbound through the stopped traffic,” Poulos said. “Colliding with all of the vehicles.”

Four big rigs and six passenger cars were involved, some too badly damaged to immediately determine their make and model, said Poulos (POH-lus).

The crash scene was “pretty overwhelming,” said Poulos, a 16-year veteran.

He said police were not releasing the identities of the four people killed until their families were notified. The injuries received by four people were not life-threatening, he said.

Traffic tie-ups extended across the state line into Louisiana.