A tractor-trailer rig slammed into a pickup truck that was stopped in the middle of a fog-shrouded rural highway early Thursday, killing six people, all students or recent alumni of a nearby community college, authorities said.

Chief Deputy Jimmy Green said two other young adults in the extended-cab pickup were injured. They were hospitalized but no information on their conditions was available.

The pickup had pulled onto Highway 26 from another highway when it was hit about 3:30 a.m. The driver of the rig was not seriously injured, Green said.

State troopers have determined the pickup had stopped and was sideways on the highway at the time, said Sgt. Joe Gazzo, a spokesman for the Mississippi Highway Patrol. He said it was unclear why the pickup's driver had stopped.

"There was a very heavy fog," Gazzo said. "The 18-wheeler came out of the fog and he couldn't see the pickup and they couldn't see him."

He identified the dead as Brittany Jordan, 18, and her sister, Carley Jordan, 20, both of Ocean Springs; and four Biloxi residents: William Thompson, Richard O'Barr and Candace Newman, all 20, and Joshua Scott Bozeman, 21.

All eight people in the pickup had attended Mississippi Gulf Coast Community College's Perkinston campus, but only O'Barr and Thompson were enrolled this semester, college spokeswoman Colleen Hartfield said. The others were attending schools including the University of Mississippi and the University of Southern Mississippi.

Wiggins is near Mississippi's Gulf Coast, 130 miles south of Jackson.