(AP) — Investigators are trying to determine why safety doors failed to close in a New York City high-rise when a deadly fire broke out. The failures allowed thick smoke to billow through the tower and kill 17 people, including eight children, in the city’s deadliest blaze in more than three decades. Fire officials determined that an electric space heater started the fire Sunday in the 19-story building in the Bronx. The flames damaged only a small part of the building, but smoke poured through the apartment’s open door and turned stairwells into death traps. The stairs were the only method of escape in a building too tall for fire escapes.