Indonesian rescuers Thursday pulled two more bodies from a river after a boat carrying timber company workers sank, bringing the death toll to three with 30 still missing, an official said.

The boat carrying 63 workers sank Wednesday after being hit by a huge wave as it travelled across the Mahakam River in East Kalimantan province in the Indonesian part of Borneo island.

"The search for survivors... is still under way," national disaster agency spokesman Sutopo Purwo Nugroho said. He said that three bodies had been recovered and 30 people had been rescued, but 30 were still missing.

Lieutenant-Colonel Junaidi M., military commander in Samarinda city near the site of the accident, said the victims drowned after being swept away when the boat went down.

A spokesman for plywood company Kalamur said high waves had caused the accident.

"Survivors told us that water got into the boat after it was hit by a big wave. Everyone panicked and ran to the front of the boat, causing it to tip over and sink," A'an Setiyawan reporters.

Boat accidents are common in Indonesia, where vessels have a poor safety record and the population of 240 million is scattered over a vast archipelago of more than 17,000 islands.