JAKARTA, September 22 (RIA Novosti) - At least 15 passengers were killed and 16 others injured when an overloaded ferry sank off Halmahera Island in eastern Indonesia, regional media said on Tuesday.

Three people are still unaccounted for after Monday afternoon's accident, media reports said.

However, a senior local police official said more than 40 people could be missing after the tragedy. Police are continuing to search for missing passengers.

Ferries are a main source of transportation in Indonesia, the world's largest archipelago nation. Sea accidents are common due to overcrowding and poor safety standards.