MILACA  (AP) — Authorities are investigating a fatal industrial accident at a gravel pit in Milaca.

The Mille Lacs County sheriff's office says 41-year-old Scott Armstrong of rural Swanville was killed Thursday while working on a large conveyor belt system that was to be moved.

Authorities say Armstrong was struck in the head by a large wheel.  The medical examiner will determine the exact cause of death.

The accident happened at a Knife River pit, where Armstrong worked as a crushing operator. A Knife River spokeswoman says the company is "devastated" by Armstrong's death.

She says Knife River plans to turn the matter over to the Mine Safety Health Administration for investigation.

Copyright 2011 The Associated Press.