Twenty-three people were left missing in Borneo after an overloaded boat capsized in treacherous rapids on a jungle river, Malaysian police said.

Sarawak police chief Acryl Sani Abdullah said 181 people had been pulled from the waters of Malaysia’s longest river, the Rajang, near the town of Belaga. At least 23 were still unaccounted for after the accident Tuesday morning.

“So far no bodies have yet been found. We stopped the operation because there is no light any more. We will resume our operation tomorrow,” he told AFP.

The boat was supposed to carry a maximum of 74 passengers. The overturned boat remained in the river and there are fears that some people may have been trapped inside. Some may have been swept downstream and managed to climb ashore, said Acryl Sani.

The passengers were believed to be heading home for the coming weekend’s Gawai festival, a major cultural and religious observance for indigenous Borneo tribes.

Officials said the boat was heading downstream and was believed to have struck a rock while navigating the rapids through the sparsely populated jungle in Sarawak, reports AFP.