Four people from a boat missing in Indonesia with more than 100 people aboard were found alive on Sunday, an official said, as rescue teams continue scouring the rough seas for other survivors.

"This morning four passengers, consisting of two men, a woman and a child, were found safe," transport ministry spokesman J.A. Barata said in a statement to AFP.

"They were taken to a hospital in Siwa," he added, referring to the town in south Sulawesi island where the stricken ferry was heading when it ran into trouble on high seas.

Barata said several search and rescue ships had been deployed to search for more survivors in the area, where waves of up to five metres (16 feet) were being recorded.

Local search and rescue head Roki Asikin said the four survivors were found clinging to fishing buoys in the rough, open seas about 15 nautical miles from the mainland.

"These waves are very high," he said.

"It took three hours to evacuate to the mainland."

Rough conditions hampered earlier efforts to locate the stricken vessel with 118 people on board -- 89 adults, 19 children and 10 crew -- after it sent out a distress signal Saturday afternoon reporting an accident.

Authorities lost contact with the ferry shortly thereafter, and it failed to arrive at its destination. However earlier reports the boat had sunk were dismissed by officials who instead claimed it was adrift having lost engine power.

There have been no reports of casualties.

There had been warnings about extreme weather in the area in the days leading up to the accident, with strong winds and rough, powerful seas.

The Indonesian archipelago of more than 17,000 islands is heavily dependent on ferry services but the industry has a poor safety record and fatal accidents are common.

Just this week a Danish cargo ship collided with a tanker and sank in Indonesia's west, with some crew still missing.