Plum, PA – An explosion flattened a house in suburban Pittsburgh yesterday, killing a man, injuring his 4-year-old granddaughter and damaging several homes nearby, authorities said.

A utility spokesman said that the explosion appeared to have been caused by the ignition of natural gas, but it remained unclear why it happened.

Richard Leith, 64, of Trafford died at a Pittsburgh hospital, said John J. Smith, an investigator for the Allegheny County Medical Examiner’s Office. Leith’s granddaughter, Gianna Pettinato, was found sitting in debris near the house next door.