Rescuers have started to dig vertically towards the 41 trapped construction workers after initial efforts to free them have been hampered by debris and technical issues.
The trapped workers have been stuck in the collapsed tunnel, in northern India, for nine days, surviving on nuts and roasted chickpeas that are being fed through a pipe.
An access road has been built on top of the hill from where the vertical drilling will start, disaster management official Devendra Patwal said.
The renewed approach should take just a few days to drill to the tunnel.
The workers have been trapped since November 12, when a landslide caused a portion of the 4.5-kilometre (2.8-mile) tunnel they were building to collapse about 200 metres (650 feet) from the entrance.
As Uttarakhand is dotted with Hindu temples, highway and building construction has been constant to accommodate the influx of pilgrims and tourists.
The tunnel is part of the Chardham all-weather road, a flagship federal project connecting various Hindu pilgrimage sites.
About 200 disaster relief personnel have been at the site using drilling equipment and excavators in the rescue operation.
The horizontal drilling effort involved a machine breaking through rocks and debris to create a space to insert pipes through which the trapped workers could crawl out, but it was halted after the machine was damaged.
The machine’s high-intensity vibrations also caused more debris to fall.
Drilling vertically from the top of the hill could also cause debris, but officials said they would use a technique designed for unstable ground.
The rescuers will need to dig 103 metres (338 feet) to reach the trapped workers — nearly double than if they carried on digging from the front.
Officials said the efforts to reach the workers from the horizontal tunnel would continue.
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