At least one person has died and dozens are missing after a ferry carrying 80 people capsized Monday in Indonesia, an official from the national disaster agency said.
"Eighteen passengers have been rescued, one is dead," said agency spokesman Sutopo Purwo Nugroho.
Authorities have deployed rescue vessels to the scene but bad weather has halted the operation for the night.
"The evacuation has been halted due to bad weather. The visibility is only 30 metres," local police chief Marudui Liberti Pandjaitan told local TV station TV One.
The boat overturned in Lake Toba in the province of North Sumatra, more than 1,300 kilometres (800 miles) north west of the capital Jakarta.
Authorities believe the craft was operating illegally with no manifest and the passengers had not been given tickets.
"This is a traditional boat that has been operating like that for years," Pandjaitan added.
Muslim-majority Indonesia has been celebrating the Islamic festival of Eid since Friday and millions go on holiday during the festivities, with Lake Toba a popular tourist destination.
The sinking is the latest in a string of deadly maritime accidents in the vast Indonesian archipelago, which relies heavily on boats to ferry people around its 17,000 islands but has a poor safety record.
Last week, a traditional wooden boat with about 40 people capsized in the island of Sulawesi, killing more than a dozen people.
In 2017, a tourist boat on the resort island of Bali exploded, killing two foreigners and injuring about 20 others.