The death of a painter who fell from a scaffold Monday at Heinz Field has been ruled an accident, the Allegheny County coroner's office said.

Russell W. Costolo, 45, of Lemont Furnace, Fayette County, was pronounced dead around 3 p.m. at Allegheny General Hospital due to head injuries. He had fallen 67 feet onto a concrete floor.

Co-workers told police they saw Costolo slip off the scaffold around 2:20 p.m. while he was painting the inside stairwell of Gate C. What caused the fall is unknown.

The federal Occupational Safety and Health Administration is investigating the incident, according to OSHA area director Robert Szymanski.

Costolo was working for Avalotis Paint Co. based in Verona.

Officials from Avalotis and the Steelers declined to comment on the nature or scope of the project on which Costolo was working, saying the accident is still under investigation.