enlarge John Ewing/Staff Photographer

The driver of the white van was killed Tuesday after losing control of his vehicle on the Maine Turnpike and crossing into the southbound lane, striking several other vehicles. Five people were injured.

State police are trying to determine why a van ran into a guardrail on the Maine Turnpike Tuesday and flipped to the opposite side of the highway, killing the driver and injuring five people who were in vehicles that crashed into the van.

The name of the van's driver was not released because police were still notifying relatives Tuesday night.

The accident began in the northbound lanes at mile 31.5, about a half-mile south of the Biddeford interchange, shortly before 10:30 a.m., said Steve McCausland, spokesman for the Maine Department of Public Safety. The van went airborne and crossed into the southbound lanes, where it hit a pickup truck and then was hit by an SUV.

The van's driver was ejected as the vehicle turned over in the air, McCausland said. The van ended up on top of the driver, killing him instantly.

The pickup truck's driver, Arthur Amirault, 61, of Merrimack, Mass., wasn't hurt. The SUV's driver, Jennifer Farrar, 29, of Charlotte, and four of her passengers -- including three children younger than 6 -- were treated and released from Southern Maine Medical Center in Biddeford. McCausland said their injuries were minor.

A witness, David St. Laurent, said he saw the van drift from the slow or middle lane, across the far left passing lane and into the guardrail. The pickup's driver swerved to avoid the van, he said, and McCausland said the van just clipped the pickup.

St. Laurent, who works at the Biddeford Car Wash, adjacent to the turnpike, said the van didn't appear to swerve suddenly, suggesting the driver might have fallen asleep or suffered a medical problem.

The accident tied up southbound traffic on the turnpike until early afternoon, said Dan Paradee, Maine Turnpike Authority spokesman.

All three southbound lanes were closed for about an hour, Paradee said, then one lane was reopened. All three lanes were open by 12:30 p.m., and traffic returned to normal by about 1 p.m.

While all three lanes were closed, traffic backed up as far as the Saco interchange, five miles north of the accident site, Paradee said. Drivers were advised to get off at Saco and take Route 1 to Kennebunk while the turnpike lanes were closed.

Northbound traffic was not affected, Paradee said.

Staff Writer Edward D. Murphy can be contacted at 791-6465 or at emurphy@pressherald.com