A UPS cargo plane’s left wing caught fire and an engine fell off just before it crashed and exploded after takeoff in Kentucky, a federal official said Wednesday, offering the first investigative details about a disaster that killed at least 12 people, including a child. Finding survivors seemed unlikely as first responders searched the charred area of the crash at UPS Worldport, the company’s global aviation hub in Louisville, Gov. Andy Beshear said. The inferno consumed the enormous aircraft and spread to nearby businesses.