Corsica, PA – CORSICA, Pa. (AP) — An unknown gas, possibly propane or methane, sparked an explosion last week that leveled a home and killed a pastor, his wife and their granddaughter, authorities said.

The explosion Friday killed Charles F. Harper, 64; Dorothy Harper, 53; and 1-year-old Bailey Harper.

Investigators said the blast in Rose Township, about 65 miles northeast of Pittsburgh, was accidental and believe it was caused by a gas. Jefferson County Coroner Bernard Snyder said fire marshals are investigating whether propane or methane are to blame.

Harper was the pastor of Seneca United Methodist Church in Venango County before retiring in the past year. The family was buried Sunday in Brookville.