Authorities battling devastating floods in Bihar ordered a probe on Wednesday to determine whether negligence contributed to the disaster, while more people drowned and diseases spread across South Asia.
Fourteen more people drowned overnight in flood-hit Bihar, raising the death toll there to 104, officials said.
So far at least 1,000 people have died across South Asia from monsoon flooding that started in June.
Anger is mounting among flood victims in Bihar, who took to the streets on Wednesday protesting against meagre food supplies and lack of safe drinking water in many areas.
Aid agencies, clearly unimpressed by the speed of relief efforts and the lack of any relief work at all in some areas, have said children and women could die soon from diseases.
"Conditions in these flood camps are terrible. People use the same stagnant water for bathing as well as washing their clothes and utensils," said Thomas Chandy, head of relief agency Save the Children in India.
"Children are playing around in this water and inadvertently drinking it and getting sick," he said.
Villagers also complained of hunger in the camps.
"We survived floods but now it looks we will die of hunger, diseases and dirt," said Rishideo Sada of Bihar's Saharsa district.
More than 3 million people have been displaced from their homes in Bihar, officials said, after the Kosi river burst a dam in Nepal, swamping hundreds of villages and destroying 100,000 ha of farmlands downstream.
But experts and aid agencies have blamed government ineptitude for not only failing to warn people but also for mishandling relief work.
In one example, emergency fax messages sent by engineers at the Kosi dam warning of impending disaster were ignored in Bihar's capital Patna, weeks before the disaster struck, a senior disaster management official said.
Faxes piled up on one bureaucrat's desk because he was on leave and no deputy had been appointed, officials said.
"We have come across such reports, and we will definitely look into this issue once all this is over," Nitish Mishra, Bihar's disaster management minister, told Reuters.
The state government said a special panel under a retired judge would investigate the allegations.
"The breach in Kosi has caused extensive damage to lives and properties and a panel will inquire whether there was any negligence by any individual, institution or government officials," said Girish Shankar, a senior government official.
Diseases stalk camps
In Bangladesh, floodwaters continued to recede but authorities reported a spike in the numbers affected by water-borne and other diseases such as diarrhoea, pneumonia and skin infections.
In the capital Dhaka, the number of diarrhoea patients has shot up to 600 from 400 within two days.
"This year we noted that the high numbers of adult patients arriving in severe states of dehydration, which may be an indication of more severe forms of the disease," said one doctor at the International Centre for Diarrhoeal Disease Research.
The deluge swept through at least 20 districts in Bangladesh, displacing nearly 200,000 people and left many more stranded in their partially submerged homes.
(Additional reporting by Ruma Paul in Dhaka)