LUCKNOW: At least 40 Indian workers trapped inside a collapsed Himalayan highway tunnel will spend a second night there on Monday, pending arrival of rescue material, after being confined for over 38 hours in a cavernous space, officials said.

Excavators have been removing debris to carve out a path to reach the workers while contact has been established with them and oxygen and food are being supplied through compression pipelines, rescue workers and police in Uttarakhand state said.

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.

Rescuers were awaiting delivery of a wide steel pipe after midnight that would then be pushed into an opening of excavated debris to safely pull out the workers in about 24 hours, said Devendra Singh Patwal, a disaster management official.

"There is enough water while oxygen and food for instant energy like dry fruits are being supplied to them," Patwal added. Local media cited another official as saying there was enough light in the space they are trapped.

The tunnel, which is 13 metres wide (43 feet) and 15 metres (50 feet) in height with the workers trapped in a two-kilometre space, was being built on a national highway that is part of a Hindu pilgrimage route, Patwal and state authorities said.

It caved in around 5:30 a.m. on Sunday (2400 GMT on Saturday). The workers are largely migrants from other Indian states and include two locals, state authorities said.

"The relief forces are removing the debris and soon we will have all the labourers out," state police chief Ashok Kumar earlier said.

About 80 policemen, 20 fire services officials and 60 disaster management officials were engaged in the rescue operations, police said.

Rescuers were communicating with workers through walkie-talkies, Kumar said, adding that the exact cause of the accident was not yet known.

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

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 889 km (551 miles) of two-lane road being built at a cost of $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.