HEBER, Utah — A truck crossed a highway median in Utah and collided with a pickup truck traveling in the opposite direction, killing all six men in the pickup in an accident authorities suspect was caused by alcohol and prescription drugs, state troopers said Saturday. Another two people were injured in a Jeep when the driver lost control trying to avoid the trucks.

The Utah Highway Patrol said investigating officers found prescription pills and open containers of alcohol inside the dump truck after the accident that occurred around noon Friday on a state highway near Heber, about 15 miles south of Park City.

The dump truck driver was treated for minor injuries and booked on suspicion of six counts of automobile homicide, the agency said.

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Utah Highway Patrol identified Efrain O Cardenas, 62, of Salt Lake City, as the driver of the pickup truck, CBS Salt Lake City affiliate KUTV reports. Medical examiners are still working on identifying the other victims.

Patrol Sgt. Lawrence Hopper said Saturday authorities were working to identify the victims.

"It was one of the most horrific accidents I have ever seen," he said.

The highway patrol reported that just before the accident another driver had contacted authorities to say that dump truck was driving erratically.

The westbound dump truck then vaulted over the middle barrier and slammed into the driver's side of the eastbound pickup, police said. Three of the men were thrown out of the vehicle and another three remained inside.

The driver of an eastbound Jeep lost control of her vehicle when she tried to avoid the two trucks and it rolled over and landed upside down, authorities said. She and a female passenger were taken to a hospital in Park City for treatment of non-life-threatening injuries.