The boat went down late on Monday close to Rote island, about 1,200 miles east of the capital Jakarta, said Piter Fina, head of the region's main port on the Indonesian side of Timor island.

At least 19 survivors had been picked up by a rescue boat, said police spokesman Martin Raja. Survivors told officials there were between 60 and 100 people on the boat when it sank.

Like many boats in remote corners of Indonesia, the ferry did not keep a passenger manifest, Raja told el-Shinta radio station.

"We have ordered all available boats to search for survivors," Fina told The Associated Press by telephone. "They have the potential to save lives."

Ship accidents are common in Indonesia, a vast archipelago where boat travel is the only way to reach many islands. Safety measures are poorly enforced, and many crafts lack enough life jackets and other safety equipment.

In March, about 40 people drowned when a ferry sunk near Rote. More than 100 were rescued by passing ships.