At least 40 people have died in flash floods inundating India's northeast, officials said Friday, as army teams plotted helicopter rescues for more of the thousands stranded in the deluge.

Violent torrents stuck the remote state of Sikkim on Wednesday after the sudden bursting of a high-altitude glacial lake near India's borders with China and Nepal.

Climate scientists warn that similar disasters will become an increasing danger across the Himalayas as global temperatures rise and ice melts.

Downstream search-and-rescue teams recovered more bodies overnight as the waters cut a swathe through the countryside towards the Bay of Bengal.

V.B. Pathak, the top civil servant in Sikkim state, told AFP that his office had confirmed 19 deaths.

Shama Parveen, a district magistrate in neighboring West Bengal, said that an additional 21 bodies had been recovered in her state over the past three days.

Roads, bridges and telephone lines have been destroyed across much of the state, complicating evacuations and efforts to communicate with thousands cut off from the rest of the country.

Nearly 8,000 others were taking shelter at makeshift relief camps set up at schools, government offices and guesthouses, according to a state government bulletin.

An Indian army statement said that soldiers on rescue operations had been able to account for nearly 1,500 people visiting from out of state who were still marooned in the worst-hit flood areas.

"There may be a window of opportunity for evacuation of stranded tourists by helicopters" with weather conditions improving on Friday, the statement added.