At least 166 people are still missing a day after a passenger boat, presumed to have been carrying over 185, capsized and sank in Indonesia's giant Lake Toba, with only one confirmed death so far, police and local military said Tuesday.

"As of now, the total valid number of passengers is still unknown. The lack of a manifest of KM Sinar Bangun has made it difficult for the authorities to determine the number of victims in the accident," the National Police said in a statement.

(Photo courtesy of the National Disaster Mitigation Agency)

Late Tuesday, the Pantai Timur military command that supervises the area issued a list of missing persons totaling 166, based on information from relatives of unaccounted-for people believed to have been on the wooden tourist boat when it sunk.

The police said the figure may increase if more relatives report their loved ones missing.

Bad weather and high waves in the lake Monday hampered rescue efforts, the police said. Only 18 people have been found alive.

The boat was on its way from Samosir, a volcanic island in the middle of the country's largest lake, to the town of Parapat, a few kilometers away, when it sank at 5:30 p.m. Monday.

(Supplied video by the National Disaster Mitigation Agency)

The 1,145-square-km lake, located in the northern part of Sumatra Island about a three-hour drive from the island's largest city of Medan, is the world's biggest volcanic lake.

It is a popular spot for local and international tourists.

No foreign visitors appear in the list of missing passengers, most of whom were believed to be Indonesian holidaymakers enjoying the country's 12-day-long Eid al-Fitr holiday.

Maritime accidents occur with some frequency in Indonesia, mostly due to safety problems such as overcapacity and bad maintenance of ships and boats.