The 61-year-old Ellwood City man who died Tuesday at a small plant that processes sewage for Prospect had a heart attack.

Butler County Deputy Coroner Larry Barr said Wednesday that an autopsy revealed fatal heart damage, not a fall or drowning, was the cause of the man's death.

State police and rescue crews were called to the plant on Park Road in Franklin Township at around 11 a.m. Tuesday for a report of “a man in a pit.”

Emergency responders remained at the plant, which is on Moraine State Park property, for several hours Tuesday as the scene was investigated.

State trooper Brian Palko declined to reveal the man's name out of respect for his family.

Prospect Mayor James Butler said Tuesday afternoon that the man was not a borough employee, and that the single treatment tank was being cleaned that day.

A Dalton's Services water tanker truck was at the unfolding scene Tuesday. Dalton's Services of Ellwood City provides septic and suction truck services, but it has not been confirmed that the man worked for the company.