WALES — The driver of a dump truck hauling gravel was killed Friday morning when the truck rolled over.

Androscoggin County Sheriff’s Office Chief Deputy William Gagne said investigators are looking into the possibility that a medical issue caused the crash.

The driver was the sole occupant of the vehicle; no other vehicles were involved, Gagne said.

Route 126 was closed to traffic for several hours, but was expected to reopen around noon, he said.

Authorities are withholding the name of the driver pending notification of next of kin.

The truck was headed in the direction of Monmouth shortly before 7 a.m. when it left the roadway and rolled over, Gagne said.

The Sheriff’s Office is conducting an accident reconstruction, which is required in all fatal accidents.

The Maine State Police Commercial Vehicle Enforcement Unit assisted at the scene, along with fire departments from Monmouth, Wales and Sabattus as well as Sabattus Police Department.

This story will be updated.