Indian authorities rushed doctors and medical equipment to flood-devastated northern India on Monday to ward off outbreaks of disease among the hundreds of thousands of victims crowding relief camps, officials said.

Nearly half of the 1.2 million people who were left homeless when the Kosi River burst its banks two weeks ago, spilling over north India's vast plains, had been rescued by Monday, and officials said they hope to reach the rest in the next three days.

About 250,000 refugees were in government and relief agency camps, said Prataya Amrit, a top disaster management official in Bihar state, the scene of the flooding. Many of the rest have taken shelter with families or friends.

Meanwhile, rescue efforts pressed ahead, led by more than 2,000 extra military personnel sent to the region.

In the Madhepura district of the state, the army, using two boats strapped together to fight the current, plucked more than 200 people off the roof of a school where they had been trapped for 11 days.

"God, who has given us so much sorrow, finally saved us," said Malti Devi, 55, as she was reunited with her son, who had camped out on the shore for over a week waiting for her.

However, amid the chaos it seemed as if there was little coordination between the rescue efforts and relief. After being dropped on the shore, the villagers had to walk 12 miles (20 kilometers) to the nearest camp.

With the numbers in the camps expected to nearly double in the coming days, there were fears the crowded and often unsanitary conditions could lead to outbreaks of diseases such as cholera.

The United Nations warned that "the heat, combined with limited supplies of safe drinking water and poor hygiene conditions, poses a great risk of water and vector-borne diseases."

In one camp set up at a school in Saharsa district -- one of the worst hit of the five flooded districts in Bihar -- a nurse was trying to treat the sick armed with just one packet of paracetamol tablets.

"We have had 35 cases of diarrhea and fever today out of 800 people in the camp," said the nurse, Niru Kumari. Saharsa is about 750 miles (1,200 kilometers) northeast of New Delhi, India's capital.

Amrit, the disaster management official, said the situation would improve greatly in the coming days.

"A lot of doctors have been moved and the Health Ministry is mobilizing," he said. "I'm sure it will be worked out in a day or two."

Officials from UNICEF, the U.N. children's agency, said the government was doing a good job getting food to the camps and bringing in doctors.

"In some of the mega camps being built there is adequate sanitation, but those are not yet complete," said Mani Kumar, an emergency specialist with the agency.

Kumar said the threat remained while people were in overcrowded temporary camps.

"We are monitoring the situation for outbreaks and are ready to rush in," he said. The agency has already distributed more than 500,000 water purification tablets and sachets of rehydration solution to treat diarrhea.

Adding to their troubles, flood waters continued to rise, inundating some camps and cutting off access to others, particularly in Supaul district near the border with Nepal. Late Sunday the main road leading to the area was washed away.

Officials say the flooding is expected to continue until November when the last of the monsoon rains taper off. Only then will they be able to plug a breach in the Kosi River that is more than a mile (kilometer) wide and growing.

The river, which flows down from the Himalayas into India where it joins the Ganges River, dramatically changed course after the breach, moving dozens of miles (kilometers) to the east and turning hundreds of square miles (kilometers) of land into a virtual lake.

Officials don't yet have a precise tally of those killed, but estimates range from scores to thousands. On Friday, 19 people drowned when their rescue boat capsized.

While Bihar, one of India's poorest states, is used to flooding from the annual monsoon, this year's floods have been particularly devastating because they have hit areas that normally remain dry and lack the infrastructure to deal with the rising waters.

The monsoon season, which starts in June, brings rain vital for the farmers of South Asia but also can cause massive destruction.

In neighboring Bangladesh, flooding has cut off at least 50,000 people, news reports said Monday, as a flood warning agency forecast the situation was "likely to deteriorate."