There were reports the Bell 412 had crashed into a mountain in North Sulawesi province, said Lucky Pondáag, an airport spokesman, adding that a search-and-rescue team had been deployed.

Eventually it became too dark to work, however, and the team decided to return early Thursday morning. The helicopter left the provincial capital of Manado at 4:26 p.m. (06:26 GMTi Wednesday, Pondaag said, and had been heading to Gosowong, a town in the Maluku islands.

Lt. Col. Vafafe Bayu, a local police chief, told TVOne six Indonesians and four Australians were on board. They apparently worked for a mining company in North Maluku.