CRESCENT, Pa. (AP) — A propane system is believed to have been the source of a massive explosion that killed two people and destroyed a house in the Pittsburgh area earlier this year, authorities said.

A spokesperson for the Allegheny County fire marshal's office told the Pittsburgh Post-Gazette that the investigation of the March 12 blast in Crescent Township had been closed and “will remain undetermined,” but “the source of the blast is related to the privately owned propane system.”

The Pennsylvania Public Utility Commission's safety division said Tuesday it had concluded its probe and found no evidence linking the blast to natural gas service under public utility jurisdiction. The home had no public utility natural gas service, and while Columbia Gas has natural gas mains in the general area, there were no utility gas mains in the immediate vicinity, and no utility gas leaks were found, the commission said.

The commission noted, however, that “while there was no public utility natural gas service connected to the home, a private natural gas well and propane tank were located on the property – which are both outside the PUC’s jurisdiction.”

Aerial images from the scene in Crescent Township in the northwest Pittsburgh suburbs showed smoking ruins with the structure reduced to rubble and some large pieces lodged in trees above. Chief Andrew Tomer of the Crescent Township fire department said the blast was “severe, absolutely extreme — ... you could feel it in your chest.” The homeowners, 89-year-old David Mitchell and 87-year-old Helen Mitchell, were killed.

In August 2023, a blast in the borough of Plum about 25 miles away in the same county killed six people and destroyed three homes. Authorities said the cause was under investigation, but the explosion occurred inside one of the homes, ruling out an outside cause including wells, pipelines and other utilities.