At least 15 people were killed on Monday after a wooden boat sank off the coast of Indonesia’s Sulawesi island, search and rescue officials said, adding that all missing passengers had been accounted for.

The boat sank with 48 people onboard just after midnight (5pm GMT on Sunday), the local office of Indonesia’s search and rescue agency said in a statement.

Six people were rescued and taken to hospital for treatment, it added, and the cause of the sinking was being investigated.

Muhamad Arafah, head of the local search and rescue agency in Kendari city in Southeast Sulawesi, said in the statement that the 27 other passengers had been accounted for and all the victims had been identified.

The agency had earlier reported that 19 were missing and that search efforts were ongoing, but Arafah said the operation had now been “declared finished and closed”.

The boat was crossing a bay between the villages of Lanto and Lagili in Central Buton regency on Muna island, said local rescue office spokesperson Wahyudin, who like many Indonesians goes by one name.

The spokesman told AFP that the passengers had previously been recorded as missing because they had “rescued themselves, and once they got on land, they went home”.

The vessel was a wooden passenger boat and not a ferry as initially reported, according to Wahyudin. He refused to confirm local media reports the boat was overcrowded.

Indonesian media reported that villagers had travelled for a local celebration and gathered on an overcrowded boat that capsized on its way back across the bay.

It is common in Indonesia for the actual number of passengers on a boat to differ from the manifest.

The rescue agency shared images of several dead bodies covered by sarongs laid on tarpaulin at a local hospital.

Marine accidents occur frequently in the Southeast Asian archipelago nation of around 17,000 islands, where people rely on ferries and small boats to travel around despite poor safety standards.

In 2018, more than 150 people drowned when a ferry sank in one of the world’s deepest lakes on Sumatra Island.

In May last year, a ferry carrying more than 800 people ran aground in shallow waters off East Nusa Tenggara province and remained stuck for two days before being dislodged. No one was hurt in that accident.