CHALLIS — A 51-year-old Ammon man died Thursday after the semi he was driving overturned on U.S. Highway 93 east of Challis, according to Idaho State Police.

The crash happened around 10:37 a.m. on northbound Highway 93 when the man was driving a 2005 Peterbilt semi hauling a gravel-loaded trailer.

The tractor-trailer drove off the right side of the road and into the borrow pit, state police said. The driver attempted to steer the semi back onto the roadway and succeeded, but the trailer remained in the borrow pit, causing the tractor and trailer to become detached, state police said.

The tractor rolled once and came to rest on its wheels while the trailer overturned onto its top, state police said.

The driver, who was not wearing a seat belt, died at the scene, police said. His name has not been released.

The crash remains under investigation by Idaho State Police.