A worker killed at Suncor's Millennium oilsands site north of Fort McMurray Tuesday morning was run over by a heavy haul truck, Alberta Occupational Health and Safety said.

The 40-year-old man was killed while he was hauling the disabled truck in for repair. His name hasn't been released. He worked as a contractor with Finning Canada.

Barrie Harrison, a spokesman for Occupational Health and Safety, said two other workers were injured in the incident.

"One was treated on site. The other was taken to the hospital, treated and released," he said. Initial reports suggested only one person was hurt.

The investigation into the incident is expected to take weeks, if not months, Harrison said Tuesday.