One person was killed in Madhepura district when angry villagers fought among themselves over limited supplies of food and medicines at overcrowded relief centres.
The Kosi river in Bihar, one of India's poorest states, smashed through mud embankments and changed course last week, unleashing huge walls of water that inundated hundreds of villages and towns.
The floods have since killed nearly 50 people in Bihar.
Torrential rains have killed more than 1,000 people in South Asia since the monsoon began in June, mainly in India's northern state of Uttar Pradesh but also in Nepal and Bangladesh.
Some experts blame the floods on heavier monsoon rains caused by global warming, while others say authorities have failed to take enough preventive measures to improve infrastructure.
Officials said flood victims had looted grains at some places in Bihar. Others ran for miles under helicopters that were dropping food packets. One boy was killed and about 30 people were injured in Supaul district when food packets fell on them.
"We have enough stock of food grains but the problem is that we have limited means of transport to supply them among the villagers," Rajesh Kumar Gupta, a government official in Madhepura, told Reuters by telephone.
Several prisoners took advantage of the floods and escaped from a jail in Supaul on Tuesday night, officials said.
"We are having difficulty in getting the exact number of prisoners who fled since communication networks have totally snapped," said Nitish Kumar, Bihar's chief minister.
The U.N. children's fund UNICEF said roads had been damaged and water and electricity supplies disrupted in the affected areas. Railway tracks have been submerged and essential commodities, including food, are being transported by boat.
FLOATING ON TREE TRUNKS
Those displaced by the floods are not expected to be able to return home for another two or three months, when the embankment is repaired and the river moves back to its normal course.
"We are appealing to villagers to evacuate the (flooded) areas," Bihar's Kumar said in a radio address on Tuesday.
"They must understand that they are right in middle of the river and the monsoon season is still in progress."
Local people call the Kosi the "Sorrow of Bihar" for its regular floods and ability to change course quickly. It originates in Nepal, where it broke a dam last week.
UNICEF said cases of diarrhoea and fever were being reported in makeshift camps.
"The weather has been extremely hot, aggravating the suffering of the displaced population, particularly for children, pregnant and lactating women and the aged," it said.
Television images showed people using banana tree trunks and cots to stay afloat, some even with their cattle and goats.
Officials said floods had destroyed more than 227,000 homes and damaged about 100,000 hectares (247,000 acres) of wheat and paddy crops.
Last year, floods in eastern India and Bangladesh killed around 2,000 people. Millions were affected and officials fear climate change will make similar disasters more frequent.
Engineers began repairing the broken dam on the Kosi river in Nepal on Wednesday to prevent it from causing further damage.