The 17-year-old driver of a minivan crammed with illegal immigrants apparently fell asleep at the wheel, causing a rollover accident that killed one passenger, authorities said.

Officials worked Wednesday to identify the 15 passengers from Guatemala (search) and Mexico (search) who were packed into a vehicle that normally seats seven or eight.

Patrol Sgt. Wade Breur (search) said there was confusion over how many people were killed in Tuesday's crash because of conflicting witness accounts. He said Wednesday that a 20-year-old Guatemalan woman was the only fatality.

The young driver, also an illegal immigrant (search), was found walking along the road about a mile away. He was turned over to immigration officials Wednesday, authorities said.

"There were no skid marks on the roadway," Lt. Todd Peterson said. "That leads us to believe the driver fell asleep."

Two people in the van were hospitalized in critical condition.