Divers and rescue workers are looking for survivors on the Brahmaputra river in India's Assam state, where a ferry capsized during a storm on Monday, killing at least 103 people.
Police said about 150 people had been rescued or swam to safety while at least 100 more were missing.
The death toll was likely to rise, Assam Chief Minister Tarun Gogoi said.
Lax safety standards mean ferry accidents are common on the river, but this is one of the worst disasters.
The accident happened in the remote district of Dhubri, about 350km (215 miles) west of Assam's main city, Guwahati.
The ferry capsized and broke into two pieces during the storm, police said.
Witnesses said many passengers were swept away by the river's strong current after the boat broke up.
Officials said they believed many bodies had been carried by the river downstream to neighbouring Bangladesh.
"I appeal to Bangladesh to help us in retrieving any dead body or survivors who could have reached their territory," Mr Gogoi said.
A passenger, Hasnat Ali, told local TV channels that about 200 people were travelling inside the boat along with cargo.
Mr Ali said he was riding on the top of the ferry with 150 other people when the storm hit, throwing off many of them.
He said he managed to hold on to a log and was rescued by villagers.
The ferry carried no lifeboats or life jackets and was overloaded with people and goods, according to a police officer quoted by Reuters news agency.
Boats are a common mode of transport in the area, which is dotted with small islands and villages along the banks of the river, reports the BBC's Sanjoy Majumder in Delhi.
Many of the boats are overcrowded with poor or minimal safety features, our correspondent adds.