Fifteen people were killed and three badly injured when a plane operated by the Indonesian police crashed into the sea off the eastern province of Papua.
The aircraft, a twin-engined Casa 212, was coming into land near the town of Sarmi when the pilot reported that one of the engines had failed.
The plane crashed 500 metres short of the runway, scattering wreckage along the shoreline.
The four crew members, all Indonesian police officers, were among the dead.
The rest of the victims were civilian passengers, including local officials.
National police chief General Da'i Bachtiar said a team had begun to investigate the accident.
Planes are often the only means of transport in the dense jungles of Papua, and bad weather and rough terrain can create hazardous flying conditions.
More than 50 people were killed in a total of four air accidents last year - three involving military aircraft.