A flash flood set off by a cloudburst wreaked havoc in a high-altitude village in Uttarakhand’s Uttarkashi on Tuesday, killing at least four persons, burying scores of others under debris and sweeping away over 50 buildings.

A torrent of sludge flattened homes, shops and hotels in Dharali in the wake of the cloudburst near the catchment area of the Kheer Ganga river, locals said. Chief minister Pushkar Singh Dhami said 70 people had been rescued and hospitalised.

Dharali is the main stopover on the way to Gangotri.

“About 50 houses were destroyed and 50 people are missing,” NDRF deputy inspector-general Mohseen Shahidi said.

According to initial reports, at least four persons have died, Uttarkashi district magistrate Prashant Arya told reporters. Many are feared trapped under the debris.

“The flash flood has washed away homes, guesthouses, hotels, homestays and restaurants in the Dharali market. The loss is too huge to be assessed at the moment. We have sought the help of the Indian Air Force and requested a few helicopters. Dharali seems to have been destroyed,” Arya said.

A source in the government said the Dharali market drew over 200 people everyday during the ongoing Chardham Yatra season.

The IAF’s Chinook Mi-17 V5, Cheetah and ALH helicopters are on active standby at the Chandigarh air base for the relief operations, air force officials said.

“We don’t know the extent of the loss of lives and properties at the moment but keeping in view the number of houses, shops, hotels, restaurants and the footfall, we can assume that it will be substantial. Reckless construction activities in the area in the last decade have turned Dharali into a geo-hazard hotspot,” said a disaster management officer on the condition of anonymity.

A disaster management officer said the treacherous hilly terrain unleashed a torrent of water, mud and boulders all of a sudden and wiped out the settlement within 10 minutes.

Experts have been warning against construction activities in the state based on the fragility of the hills and the melting glaciers in the adjacent Himalayan range.

“A flash flood in the Bhagirathi has also swept away a part of the army base in nearby Harshil, 7km from Dharali. SDRF and NDRF personnel couldn’t reach the spot even after two and a half hours, dimming hopes of rescuing the people trapped there,” the disaster management officer said.

Government sources said 8-10 army personnel from the Harshil camp were missing.

He said several jawans of the army and the Indo-Tibetan Border Police were engaged in the rescue effort.

“When we reached Dharali at 6pm, it was already dark and nothing much could be done. Still, the rescuers had brought out around 20 people alive,” the officer added.

Rajiv Swaroop, inspector-general of Garhwal, said over 150 rescuers would continue the search for the missing through the night.

Former chief minister Harish Rawat said: “Dharali was a modern village where a large number of people used to live. Several migrant labourers also used to stay there. We will be able to know the actual number of casualties when we start counting the houses that have turned into rubble and those who have survived.”

He said Dharali was on the Chardham route and devotees bound for Gangotri and Yamunotri used to halt there.

“The Dharali market is buried under a 20-metre layer of debris and rubble after the flash flood. There is every possibility that several people are buried under it,” Rawat said.

Videos purportedly recorded from a nearby hillock showed a couple of people trying to claw their way out of the debris.

Dharali is located 19km from Gangotri, 270km from Kedarnath and 402km from Badrinath.

Environmentalist Ravi Chopra said: “A cloudburst causes an enormous amount of rainfall across a limited area within a short span of time. But the impact of the flash flood could have been lessened by the dense forest cover in the hills. I believe that a huge glacial wall might have melted in the upper reaches of the Himalayas and triggered the flash flood.”

He said the high court had directed the state government after the 2013 Kedarnath deluge not to allow any construction near rivers, nallahs and hills, but neither the government nor the residents took it seriously.

Geologist Ajay Paul said: “All we can do to avoid suffering losses of such magnitude is to follow the norms and stay away from the rivers and nallahs that are prone to flash floods. The area had been witnessing incessant rain for the past few days.”

Environmentalist S.P. Sati said Dharali was destroyed in a flash flood in 1835.

“The present Dharali was built over its debris. But we are still unable to understand the sensitivity of the Himalayan region. The government acquires land in the name of development and people construct buildings without an environmental impact assessment.”

Anil Baluni, a BJP MP from Pauri Garhwal, told reporters outside Parliament: “We pray to Badrinath that there is minimum loss of lives and properties.”