Utah Highway Patrol troopers Tuesday were trying to determine what caused a fatal semi-trailer rig accident on Interstate 80 near the Echo Canyon exit.

UHP Corporal Todd Johnson identified the victim as Robert D. Carpenter, 46, of Caldwell, Idaho.

The crash occurred about 8 p.m. Monday when the eastbound semi struck the freeway's cable barrier on a curve and overturned, landing in the westbound lanes. Carpenter, who was not believed to have been wearing his seatbelt, died of his injuries despite efforts of passers-by and paramedics who attempted CPR at the scene.

Westbound traffic near mile post 172 was detoured onto a frontage road for several hours while troopers investigated and the wreckage was cleared.

Johnson said the accident's cause continued to be under investigation, but troopers suspect Carpenter may have experienced an unspecified "medical issue" at the time of the crash.

remims@sltrib.com