Porter Township, PA – New Bethlehem – Authorities in western Pennsylvania said natural gas sparked an explosion that leveled a house and critically injured a woman and her two daughters, one of whom had to be pulled from the burning wreckage Thursday morning.

The explosion around 6:30 a.m. rocked the rural Clarion County town of Porter Township and neighbors and passers-by rushed to the splintered and burning home. There they found 35-year-old Kelly Hopper and her 4-year-old daughter outside and pulled Hopper’s 8-year-old daughter free.

Kelly Hopper and her older daughter, Alexandra, were taken to Mercy Hospital in Pittsburgh, where they were listed in critical and serious condition respectively. Hopper’s other daughter, Hanna, was taken to Children’s Hospital in Pittsburgh where she was listed in critical, but stable condition.

New Bethlehem Fire Chief Barry Fox said natural gas caused the explosion, although state police fire marshals, the state Public Utility Commission and Equitable Gas are investigating.