A helicopter carrying 10 people, including four Australians, lost contact with authorities minutes after takeoff Wednesday in eastern Indonesia, police and airport officials said.
There were reports the Bell 412 had crashed into a mountain in North Sulawesi province, said Lucky Pondaag, an airport spokesman.
A rescue team called off its search after dark and will return early Thursday morning.
The helicopter left the provincial capital of Manado at 4:26 p.m. (06:26 GMT) 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.
Indonesia, a sprawling archipelagic nation of nearly 240 million, has been plagued by transportation accidents in recent years, from plane and train crashes to ferry sinkings. Overcrowding, aging infrastructure and poor safety standards are often to blame.
On Wednesday, in an area that has been the scene of a decades-long separatist insurgency, unidentified gunmen opened fire on a military chopper, killing one soldier.