Dozens of construction workers are feared trapped after the road tunnel they were building collapsed in northern India’s Uttarakhand state, with rescuers scrambling to reach them beneath piles of debris.

“About 40 to 41 workers are trapped inside. Oxygen is being supplied through the debris, but more rubble is coming down as rescuers try to remove the obstruction,” State disaster response official, Durgesh Rathodi, told the AFP news agency.

Local media, however, reported that up to 36 people were believed to be trapped in the tunnel, which partially collapsed at 4am on Sunday (22:30 GMT on Saturday) as a result of a landslide. Nearly 200 metres (14.8 feet) of the 4.5km (2.8-mile) long tunnel appear to have caved in, according to media reports.

The incident occurred during a shift change at the Yamunotri national highway in the Himalayan state when a group of workers were moving out and replacement workers were going in.

The tunnel is being constructed between Silkyara and Dandalgaon to connect two of the holiest Hindu shrines of Uttarkashi and Yamnotri.

Photographs released by the government rescue teams showed huge piles of concrete blocking the wide tunnel, with twisted metal bars on its broken roof poking down in front of the rubble.

“Pray to god that those workers trapped inside the tunnel are brought out safely,” Uttarakhand Chief Minister Pushkar Singh Dhami wrote on social media platform X.

A local police officer told the Press Trust of India news agency they were “very optimistic” the men would be rescued safely, but added it was “difficult to say how long it will take”.

Accidents on large infrastructure construction sites are common in India.

Earlier this year, Indian authorities evacuated hundreds of people from their homes in Joshimath town, also located in Uttarakhand state, after buildings in the area popular with pilgrims and tourists developed cracks.

In 2021, more than 200 people, most of them construction workers, were killed after part of a glacier broke away sweeping away two hydroelectric projects in Raini village of Uttarakhand state.

Construction of major roads to improve access to religious sites and the Chinese border area, as well as the building of tunnels, are believed to be some of the reasons behind the landslides and glacier bursts. (Al Jazeera)

•The tunnel is being constructed between Silkyara and Dandalgaon to connect two of the holiest Hindu shrines of Uttarkashi and Yamnotri [File: Dar Yasin/AP]

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