Sikkim flash flood: 36 bodies recovered with more 70 still missing

Rescue and relief work under way after several villages swept away in valley in north-east India

Indian authorities have recovered at least 36 bodies from the slush and ruins left from the flash floods in Himalayan Sikkim state but are anticipating a rising death toll as more than 70 people are still missing.

Seven of the dead were soldiers, police told The National, as search and rescue operations continue. Eighteen soldiers remain missing, they said.

As many as five districts of the tiny but ecologically sensitive state have been submerged in slush and floodwaters after the level of Teesta river overflowed by up to six metres after a cloudburst hit the Lhonak Lake area in the north-west of the state.

The lake is a bullet-shaped reservoir at the foot of a melting glacier around Kanchenjunga, the world's third-highest mountain.

The flooding caused a crack in Chungthang dam, part of a 1,200-megawatt hydroelectric power plant – the state’s biggest – sending a torrent of water cascading into the valley below, submerging several towns in the Teesta basin.

Dozens of bridges collapsed and part of a motorway was swept away.

“We are expecting the death toll to rise as we are receiving more complaints of missing people,” police inspector Wangchuk Bhutia told The National. "Many bodies have been swept away and one was recovered from Cooch Behar district bordering Bangladesh.

Buildings are inundated after flash floods triggered by sudden heavy rainfall swamped Rangpo town in Sikkim, India. AP

Mr Bhutia said several videos of bodies were being circulated on social media, some of which families had identified but authorities were unable to locate their whereabouts.

“We are not able to find out where these bodies have been recovered but our efforts are ongoing,” he said.

In Chungthang town, which was worst hit, an emergency response team was unable to land its helicopter due to bad weather.

The breach of the dam prompted the release of 5.08 million cubic metres of water that hurtling down the mountains.

Senior government official Hem Kumar Chetri said of the area below: “It is full of slush. Damage has been extensive."

Residents assess damage after flash flooding in Rangpo town in Sikkim. AP

More than 18 bodies have also been recovered from Jalpaiguri district in neighbouring West Bengal state after they were swept downstream.

Teesta river flows down from Sikkim to West Bengal before it reaches Bangladesh.

“The river stretches up to 86 kilometres here and rescue and search are under way,” A Chakraborty, a disaster-management official in Jalpaiguri, told The National.

“We have pressed teams of police, civil defence and disaster management, among others. We are keeping a close vigil.”

The Indian Space Research Organisation that released dramatic images of the lake said about 105 hectares of area had been drained since the dam breach.

Satellite images of Lhonak Lake in north-eastern India before and after the catastrophic flooding. Reuters

Flash floods are common during India's monsoon season, which starts in June and usually ends in September. However, climate change is increasing their frequency and severity, according to experts, with a rise in climate-related natural disasters in the Himalayan region that stretches 2,500km through a dozen states.