A Missoula man, 26, was killed late Wednesday night when his vehicle struck a guard rail west of Missoula on LaCasse Lane just off Mullan Road.

Montana Highway Patrol Trooper Jake Parks said the accident occurred just before midnight.

"The accident occurred on LaCasse Lane, just east of Mullan Road," Parks said. "The vehicle, a 1996 Subaru Outback, was eastbound on LaCasse and it left the right side of the roadway and impacted a bridge guardrail, and then overturned in the irrigation ditch. The occupant, a male in his mid to late 20's, was not wearing his seat belt, but was not thrown from the vehicle."

Parks said the investigation was continuing late Thursday afternoon to determine the cause of the accident, and that it was unknown if either speed or alcohol were contributing factors.

The victim's name has not yet been released.

Montana Highway Patrol Trooper Jake Parks