He said the aircraft had departed from Oroville, California, on a scheduled flight to Bozeman but the pilot had cancelled his flight plan at some point and headed for Butte.

The National Transportation Safety Board and the FAA will be investigating the crash, added Fergus.

The local Montana Standard newspaper, citing witnesses' accounts in an online story, said the plane crashed into a cemetery.

Martha Guidoni, who was at a petrol station across from the cemetery, said the plane "just nose-dived into the ground".