(CNN) -- The grinding misery triggered by the massive floods in a downtrodden part of northeastern India and across the border in Nepal persisted Friday, with government and aid agencies swinging into action to help the 2 million-plus people fleeing high-rising, fast-moving waters.
"It's not getting better. It's definitely getting worse," said Jennifer Poidatz, country representative for Catholic Relief Services. "This is water moving very rapidly."
"The water is rising by the minute," CNN Correspondent Sara Sidner said from Bihar's Supaul district, considered the worst-hit area of India.
"These are the some of the worst floods in generations, and they present a huge challenge for governments and humanitarian organizations," said Daniel Toole, UNICEF's regional director for South Asia.
The tragedy started after "the Kosi River broke a dam in Nepal and the waters breached mud embankments last week in India's Bihar state," UNICEF said, describing the flooding as one of the worst in the region in 50 years. It also reported an official death toll of 55, although it said the figure would be rising.
Water gushed through the breach so forcefully that the river changed course in Bihar, plowing a new channel about 75 miles (120 km) east of its river bed. The river was about 3 miles (5 km) wide.
There are estimates from India that 2.7 million people in 1,600 villages have been affected, thousands of them marooned on thin strips of land peeking out from the cloudy brown water of the swollen Kosi River.
UNICEF says the floods have "destroyed almost a quarter of a million homes affecting at least 1.4 million people" in Bihar. The number of displaced in Nepal totals 70,000.
Relief efforts have been hampered by damaged roads and submerging of railway tracks and many essential supplies have to be delivered by boat.
The agency is mobilizing to help the displaced and is working with the government to deliver supplies and services: food, medicine, clean water, access to sanitation, halogen tablets and salt packets.
The agency said families are crowding into relief camps, but UNICEF warns that such camps could become overcrowded and that people there could be at risk to communicable diseases.
The Indian government said it is providing as much assistance as possible to Bihar authorities, such as army troops, helicopters, boats, grain and halogen tablets. Indian Prime Minister Manmohan Singh has announced immediate aid of about $238 million and promised delivery of 125,000 metric tons of grain to the region.
Medecins sans Frontieres is doing an assessment for humanitarian needs in the region.
Sidner said the Indian army deployed troops to the region to help displaced and stranded people. She saw the army using two motorboats to ferry people from one end of the river to another because a bridge over the river was submerged.
U.S. Ambassador to India David C. Mulford announced contributions of $100,000 to the Prime Minister's National Relief Fund and Catholic Relief Services.
Caroline Brennan, a Catholic Relief Services spokeswoman, said the hard-hit regions aren't regularly hit by monsoons, so the people in these poverty-stricken areas are particularly unprepared.
Poidatz underscored this point, saying people were caught off-guard by a river that "completely changed its course because of the breach." She said the challenge for relief workers is figuring out how to help a population constantly in transit because of fast-moving waters.
Poidatz and Brennan said the government of India has been quick to respond with air drops and coordinating rescues.
"The government of India is moving huge quantities of food to the area, but we need to complement these efforts," Brennan said.
The agency is purchasing high-energy biscuits for 25,000 families and is supplying four boats for rescue, she said.
On Thursday, Indian federal and state governments released conflicting death tolls for Bihar, and there have been no updates Friday.
National disaster officials at the Ministry of Home Affairs reduced their death toll from 87 on Wednesday to 47 on Thursday, saying they previously released an incorrect tally.
K.K. Agarwal of the Disaster Management Department in Bihar released a death toll of 12, an increase of two since Wednesday.
CNN's Joe Sterling and Sara Sidner contributed to this report.