Emergency workers have drilled a third of the way through the debris blocking a tunnel in northern India where at least 40 workers have been trapped for more than 120 hours.
Authorities have tried to create a passage by inserting a 900mm diameter steel pipe for the workers to crawl through.
Emergency personnel must drill through about 60 metres of debris to insert the pipes.
The rescue teams, which include the state disaster response force, police and engineers, worked overnight on Thursday, using a drilling machine to penetrate about 21 metres of debris, Devendra Singh Patwal, a disaster management officer, told The National.
Authorities on Wednesday flew the US-made “horizontal dry drilling equipment with auger” from New Delhi to the site of the collapse, after the initial drilling machine broke down after hitting a boulder.
The collapse happened early on Sunday as a group of workers was leaving the tunnels and others were heading inside to begin their shifts.
The trapped workers are being provided with water, oxygen, electricity and small packets of food packets using a pipe, authorities said.
“They confirmed the receipt of food items. All the stranded workers are safe,” National Highways and Infrastructure Development Corporation, the agency building the tunnel, said in a statement.
The tunnel is part of the Indian government's Char Dham project, which aims to improve routes between four Hindu pilgrimage sites in the state.
Uttarakhand is home to dozens of major Hindu temples. It is a popular tourist destination and an ecologically sensitive region that has been affected by climate change.
Initial reports suggested the collapse was caused by a landslide, but an investigation is under way.