He said at least three foreigners were believed to be on the boat, which left late on Wednesday for the island of Nias, a popular spot for foreign surfers. It was unclear whether they had been rescued.
The first group of survivors arrived at Sibolga port and were taken straight to a hospital.
Hundreds of worried people waiting for news of relatives flocked to the boats and hugged their loved ones.
Accidents at sea 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 sufficient life jackets and other safety equipment.
RSS