Canonsburg, PA- CANONSBURG, Pa. – A light switch triggered a gas explosion that leveled a two-story home in a quiet suburban neighborhood, state police said Wednesday.

John Semple, 49, was pulled from the rubble by neighbors Tuesday and was in serious condition Wednesday at a Pittsburgh hospital. He suffered severe burns in the explosion.

Only the flagpole was left standing outside the home, which was destroyed.

Natural gas from a medium-sized gas line followed sewer pipes back into the home and was ignited when Semple flipped a switch to turn on a light, state police said.

The house exploded around 5 p.m., trapping Semple, Bell said. Semple’s father helped pull him from the wreckage.

“From what I’ve seen, I don’t know how anybody came out of there,” said R.T. Bell, police chief in Canonsburg, about 15 miles southwest of Pittsburgh. “There are no walls left. It’s is just gone. The roof just came down.”

Workers from Columbia Gas had been searching for the source of reported natural gas odors Tuesday afternoon.

The neighborhood’s gas service had been shut off that morning because a landslide triggered by heavy rains ruptured a gas line, allowing gas to seep into a nearby sewer line, emergency officials said.