Washington  - Investigators suspect that overloading might have caused the crash of a small passenger plane that killed 14 people, including seven children Sunday, broadcaster ABC reported Monday.

But because the single engine Pilatus PC-12 was not required to carry a black box recording device, it may be difficult to ascertain the exact cause of the deadly disaster.

The single-engine propeller plane had departed from California, and was headed to Bozeman, Montana, on a family ski-trip. But it changed its destination at the last minute and tried to land in Butte, where it crashed near the Holy Cross cemetery, about 170 metres short of the landing strip about 2100 GMT, according to local media reports. It was not clear why the pilot changed his destination.

Seven investigators were combing the cemetery Monday where the plane crashed, searching for clues to the accident. Witnesses reported seeing the pilot making sharp turns just before the plane nosedived into the ground. There was no radio call made by the pilot and it remains unclear whether there was an emergency situation that led the pilot to land in Butte.

The plane was certified to carry 12 people, but 14 people were on board. The plane was also not registered to carry commercial passengers. (dpa)