Uttarkashi district’s top civil servant Abhishek Ruhela said on Tuesday that “whatever is necessary for their survival is being done”.

Karamveer Singh, an official with the National Disaster Response Force, said rescuers had established contact with the stranded workers using walkie-talkies, and in one case a written message on paper was sent through the pipeline to communicate with them.

“We have been supplying food, water and oxygen to the trapped labourers and the officials are in continuous touch with all of them,” said Devendra Singh Patwal, a disaster management official.

He said it was not easy to ascertain the time required for the rescue, and said a team of geologists had arrived to determine the cause of the accident.

A government official said the tunnel collapsed due to a landslide. Most of the workers stuck inside were migrant labourers from across the country.

Lakshmi Pakhirai, the mother of a man called Souvik, said she was told rescuers have spoken to him. “They said he is fine and healthy.”

There were around 50 or 60 workers inside the tunnel but around 10 or 20 got out when their shift ended as they were closer to the exit, with the rest trapped after the collapse, the Indian Express newspaper reported, quoting a worker who made it out safely.

“Initially, we thought it might be a minor collapse and began removing the debris however we could,” said Rajeev Das, the worker. “But soon we realised it was a challenging search and rescue [mission].”

The region is prone to landslides, earthquakes and floods and the incident follows events of land subsidence in the state that geologists, residents and officials have blamed on rapid construction in the mountains.

The work on the tunnel stretch commenced in 2018 and was initially intended to be completed by July 2022 but has been delayed to May 2024, an Indian government statement said.

Controversial project

The Char Dham pilgrimage route is one of the most ambitious projects of Prime Minister Narendra Modi’s government. It aims to connect four important Hindu pilgrimage sites of North India through an 889km (551 miles) road costing US$1.5 billion.

But some work has been halted by local authorities after hundreds of houses were damaged by subsidence along the routes, including in Uttarakhand.

The project has faced criticism from environmental experts.

The impact of the project on areas along the route was not properly assessed before construction started, a report by a Supreme Court-appointed expert committee had said in July 2020.

When it approved the Char Dham road in 2021, the Supreme Court said wider roads would be beneficial for the defence of India’s borders.

It cautioned, however, that the government should heed concerns raised by the committee, and draw up a concrete strategy to protect the environment.

The head of the panel quit last year saying he was frustrated its recommendations were not implemented.

The federal government has publicly said it employed environmentally friendly techniques in the design to make geologically unstable stretches safer.

Uttarakhand Chief Minister Pushkar Singh Dhami on Tuesday told ANI news agency that the state would examine work at all tunnels under construction to ensure they are completed safely and authorities are better prepared to face possible emergencies.

Uttarakhand sees a huge flow of pilgrims and tourists every year to visit the temples, with the numbers expanding over the years due to the continuous construction of buildings and roads.

Accidents on large infrastructure projects are common in India.

In January, at least 200 people were killed in flash floods in Uttarakhand in a disaster that experts partly blamed on excessive development.

Additional reporting by Associated Press