NEW DELHI, India (CNN) -- Floodwaters raged through more than 1,000 villages unaccustomed to high water after a river in northeast India burst its banks, UNICEF India and government officials said Tuesday.
UNICEF said 33 deaths had been reported since the mile-long (2 km) breach in the Kosi River on August 18, and more fatalities were expected.
The water flowed through places normally not deluged during the monsoon season, which lasts from June to September.
The aid agency said more than 1.4 million people are affected in 13 districts of Bihar, and more than 225,000 homes have been destroyed. Hot weather was adding to the misery, UNICEF said.
Video showed residents in Bihar state seeking refuge on low-rise buildings, and standing in waist-high water in the streets. Many villages were wiped out, said Nitish Mishra, Indian minister for disaster management.
Mishra said 2 million people were displaced, and the government was trying to evacuate at least half that many. Watch survivors find safety on roofs »
The worst hit districts were Araria, Madhepura, Supaul and Purnea. He said there was no official death toll, but local reports placed it at more than 30.
"Roads have been damaged and water and electricity supplies in the affected districts have been seriously disrupted. Railway tracks have been submerged and essential commodities, including food, are being transported by boat," said a statement from UNICEF.
"Those displaced by the flooding are not expected to be able to return to their homes for another two or three months when the embankment is repaired and the river moves back to its normal course. Until then, these people will need to stay in relief camps," the statement added.
Several India air force helicopters were air-dropping relief supplies, Mishra said, and relief camps were set up in the Araria district.
Weather forecasters were predicting more heavy rain over the next four or five days.