As at 5pm, police have confirmed that 181 people from the boat are safe, however 23 more are still missing.
"The search and rescue mission is still being conducted at the moment," said Belaga district police chief
DSP Bakar Sebau.
Bakar also told Astro AWANI that initial investigations show that the main cause of the accident was that the boat was overloaded and had collided with some rocks at the Rajang River.
BEFORE: Photo shows passengers boarding at the Belaga jetty prior to the incident.
The accident, which is believed to be one of the worst in several decades, happened after the boat crashed onto rock in the Rajang River about 40 minutes of leaving Belaga town.
The express boat was on its way to Kapit and Sibu.
To make matters worse, the boat was carrying excessive passengers.
The express boat - which is believed to be able to carry 67 passengers - may be carrying more than 200 passengers.
Bernama reported that some 21 people are still missing while 181 others managed to swim to safety.
The express boat was extremely packed with timbercamp, oil palm and timber plantation workers returning home for the Gawai Dayak festival this weekend.
Gawai is one of the most important festivals celebrated each year by Borneo's dozens of indigenous tribes and other ethnic groups. Every year during Gawai festival, thousands of people travel to meet their friends and family.
According to a Bernama report, a councillor of the Kapit District Council Betek Lahang said the police and other related government departments assisted by timber camps, oil palm and timber plantation officials were still trying to work out the actual figures.
In a The Borneo Post report, it said that Belaga state assemblyman Liwan Lagang witnessed the accident as he was on his way to Kuching via helicopter.