EL CAJON, Calif. (AP) — Federal investigators say a medical transport plane struck power lines in cloudy weather before it crashed last month near San Diego, killing two flight nurses and two pilots.

The Learjet 35A crashed on Dec. 27 while preparing to land at Gillespie Field in El Cajon. A preliminary report by the National Transportation Safety Board says the weather was cloudy and misty when the plane struck power lines and then crashed into the yard of a home near the runway.

However, it didn't indicate the exact cause of the accident.