Littlestown, PA – Two out of the four firefighters injured were flown to a hospital Friday morning after a house exploded from an apparent natural gas leak.

Littlestown police Chief Charles Kellar said Columbia Gas workers were called to the home in the 300 block of Lexington Way after a neighbor reported fumes. Because no one was home, police were called to open a door.

The firefighters made their way inside and headed for the basement.

“And all of a sudden there’s an explosion,” neighbor Jason Beal said. “It blew out the windows, the doors, and right behind that there was another explosion.”

Firefighters Raymond Boyd and Jay Ingle sustained burns to their hands and face but are expected to be OK. Two other firefighters sustained minor injuries.

A next-door neighbor was standing outside while it happened, and stepped in to help.

Kellar said the homeowner is staying with family.

Investigators said they don’t believe they’ll ever be able to pinpoint what caused the explosion.