First Air Marshal Eddy Suyanto, commander of the air base in Makassar, said a new report had been received that an emergency signal had been picked up south of Manado, the lost plane's scheduled destination in North Sulawesi province, three days ago.

Until now, military and civilian aircraft have been mainly scouring the jungles and rugged mountains of western Sulawesi, while ships searched the Makassar Strait between the islands of Sulawesi and Borneo.

Heavy rains and strong winds have hampered the search and the rough terrain has made communication and transport difficult.

Government officials have apologized for erroneously saying on Tuesday that the 17-year-old Boeing 737-400, operated by budget carrier Adam Air, had been found and 12 people survived.

The missing plane was carrying 96 passengers, including three Americans, and six crew. Portland's Oregonian newspaper identified the Americans as wood-products executive Scott Jackson, 54, and daughters Stephanie, 21, and Lindsey, 18.

Two Singaporean Fokker-50s have joined Indonesian military aircraft in the search, while three ships are participating and another is on the way, Suyanto told Reuters earlier in the day.