A well pad at Suncor Energy's Firebag in situ oilsands project. (Suncor Energy)

An oilsands worker is dead after a workplace accident north of Fort McMurray, Alta.

Pam Sharpe with Occupational Health and Safety said the accident happened at Suncor Energy's Firebag site at about 4:15 p.m. MT.

"Yesterday ... a 55-year-old man was working on a well pad [when] a piece of equipment came loose and struck him in the chest," Sharpe said.

"He was transported to hospital with serious injuries and he has since passed away."

The man worked for Flint Transfield Services. His name has not been released.

Sharpe said all work has been halted on the well pad.

She said investigators are working to determine what caused the accident, and whether workplace safety codes were being followed. It is not yet known what type of equipment hit the man.

It it not clear how long the investigation could take.