"The boat was overcrowded because people panicked to be rescued and clambered on board," Bhaskar told The Associated Press.
The death toll from this year's monsoon season across India has surpassed 800. Some 1.2 million people have been marooned and about 2 million more affected in Bihar state, where the Kosi river has burst its banks and submerged all roads leading to the region. India's Prime Minister Manmohan Singh has described the flooding as a national calamity.
Rising waters have swept away and drowned at least 75 people in Bihar state since June, the start of the monsoon season, said Prataya Amrit, secretary of the state's disaster management department.
Authorities have rescued nearly 140,000 people and put most of them in state-run relief camps, Amrit said.
The situation was getting worse because of heavy rain in the region and a Kosi river breach on the Nepalese side, Amrit said Saturday.
"We can't assess the extent of the damage. It is colossal," he said. "But we will only be able to tell the extent after the water recedes."
The Indian government has made more than $200 million available to combat monsoon flooding. Nearly 1,500 soldiers have boosted rescue efforts in Bihar state and air force helicopters were dropping food to hundreds of thousand of people stranded by the rampaging river.
India's monsoon season, which lasts from June to September, brings rain vital for the country's farmers but often also causes massive destruction.
Despite the rescue operations under way, officials in Bihar have warned that the real danger is still ahead.
When the swollen Kosi river burst its banks in Nepal just north of the Indian border, it changed course, flowing through a fresh channel 75 miles to the east that has no protective embankments. The river traditionally swells to a flood peak in October.
In 2007, monsoon floods killed more than 2,200 people across South Asia and left 31 million others homeless, short of food or with other problems. The United Nations called last year's floods the worst in living memory.