Twenty-three people are missing in remote Kalimantan Island after a boat overloaded with holidaymakers heading home for a festival capsized on Tuesday in treacherous rapids on a jungle river, Malaysian police said.

The accident occurred on Malaysia's longest river, the Rajang, which flows from deep in the rugged interior of Borneo in the state of Sarawak.

Sarawak police chief Acryl Sani Abdullah said 181 people had been rescued, but 23 were still unaccounted for after the accident in the morning. The boat was supposed to carry a maximum number of 74 passengers.

"So far no bodies have yet been found until 6 pm this evening when we stopped the operation because there was no light anymore. We will resume our operation tomorrow," he said.

The overturned boat remains in the river and there are fears that some people may have been trapped inside. Acryl Sani said some may have been swept downstream and managed to climb ashore.

The accident happened near the town of Belaga, deep in the wild and sparsely populated interior of Sarawak, one of two Malaysian states located on Borneo.

Rom Kulleh, an aide to a local Belaga politician, said that he saw the overturned and mostly submerged boat in the river while flying over the area in a helicopter.

"The boat was stuck in the water. It was upside down," he said, adding that some of those rescued were plucked from the water by passengers aboard other boats plying the river.

Most passengers were believed to be heading home for the coming weekend's Gawai festival, a major cultural and religious observance for indigenous Borneo tribes that triggers heavy travel in Sarawak.

Officials have said the boat, which set off at the Bakun dam, was heading downstream and was believed to have struck a rock while navigating one of many rapids on the 560-km waterway.

Sarawak is Malaysia's largest state by area but also one of its least developed.

Gawai is one of the most important festivals celebrated each year by Kalimantan's dozens of indigenous tribes and other ethnic groups, with thousands traveling to meet family and friends for the occasion.

Boat operators often come under intense pressure from travelers demanding to be allowed on board so they can reach their destinations in time for the festival, said Belaga police chief Bakar Anak Sebau.

Many members of the indigenous tribal groups who predominate in Sarawak still live in traditional wooden longhouses in the jungle, where fast-flowing rivers are the quickest mode of travel.

Thirteen people died in the last major boat accident in Sarawak two years ago.

(China Daily 05/29/2013 page10)