PITTSBURGH — Authorities in Western Pennsylvania say a worker killed at a sewage treatment plant died of injuries from a fall down a 30-foot underground shaft and not as a result of toxic fumes.

The Allegheny County medical examiner's office ruled the death of 31-year-old Jack Hogan III of Baden accidental. But officials said it could be another five months before tests determine whether any noxious gases affected him before his death.

Officials said three other workers who tried to rescue Hogan on Thursday at the Sewickley plant were overcome by gases.

Investigators from the federal Occupational Safety and Health Administration and other officials are trying to determine whether safety protocols were followed. The plant is still operating.

Construction is to continue today on a $5 million upgrade that Hogan was working on.