Recent severe floods in northern India have claimed at least 822 lives while efforts to rescue thousands of stranded survivors have been made increasingly difficult because of the ongoing bad weather.

Throughout the week, rescue missions have been repeatedly grounded due to heavy rains and fog and on Tuesday a rescue helicopter crashed during a medical mission, killing all 20 people on board.

Mass cremations of the recovered bodies have begun, after concerns grew about the spread of diseases. DNA samples, belongings and photographs are being retrieved so that families can be informed.

Zubin Zaman, Humanitarian Manager for Oxfam India said he was worried about outbreaks of water-borne diseases, “We are getting reports from the field that there are rotting bodies lying around…There are also carcasses of livestock in rivers and streams and this has, of course, contaminated so many of their water sources. But people are desperate and are being forced to consume water they wouldn’t otherwise.”

Although the official death toll now stands at 822, the final number is expected to rise with hundreds still missing. The home minister said on Monday that the number was closer to 1000 deaths, while Spanish news agency EFE has reported it could be as high as 10,000 people. Tourists are also believed to have been caught up in the disaster.

An official with the National Disaster Management Authority said: “It’s very difficult to know the real figures and the scale of the disaster at the moment as many places are still blocked and we are still struggling to get to all the affected areas.”

It is believed that some 96,000 people have been rescued by a 10,000-strong armed forces team in a disaster dubbed a “Himalayan tsunami” by media.

People normally leave the area, on the edge of the Himalayas, in early July just before the rains arrive. This year’s sudden downpour meant tens of thousands were trapped as bridges and roads were washed away.