The Niagara County Sheriff's Office says the blast occurred around 6 a.m. Tuesday at a home in the rural town of Wilson, on Lake Ontario about 30 miles north of Buffalo.
Undersheriff Michael Filicetti says Sarah Johnson's body was found in the debris. Authorities aren't sure of her age but believe she was between 12 and 14.
Filicetti says her parents and two siblings were blown clear and were found in the front yard by the first deputy to arrive on the scene. He says all four are being treated at a Buffalo hospital for serious injuries.
Authorities say the home used propane tanks but the cause of the explosion isn't known yet.