Indonesian authorities say 18 people are dead after a passenger ship capsized in the waters off Borneo Island.

A local port authority official said a search and rescue operation was underway Tuesday for another 18 passengers who are still missing.

The official said the vessel sank Monday when it was overcome by heavy winds and waves near South Kalimantan province. The ship was carrying four crew members and at least 100 passengers at the time of the accident.

With over 17,000 islands, the Indonesian archipelago is heavily dependent on sea travel, but the sector has been marred by several fatal accidents over the years due to poor safety standards.