Arnold Dix, an international expert assisting the rescue in northern India, said: “The machine is busted.
“It is irreparable. The mountain has once again resisted the auger.”
Rescuers were just 30ft from breaking through to the workers before the auger broke, wedging the broken piece of equipment inside the tunnel.
As a result, workers will drill by hand to avoid the auger repeatedly getting stuck on pieces of metal in the debris, and as it would take days for a replacement to arrive.
Pushkar Singh Dhami, the chief minister of Uttarakhand, said the damaged machine would be removed by Sunday.
Syed Ata Hasnain, a member of the National Disaster Management Authority, said the operation was becoming “more complex” and the process would become slower, compared to when the auger was used to drill.
He added: “We have to strengthen our brothers stuck inside.
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“We need to monitor their psychological state, because this operation can go on for a very long time.”
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Inside India tunnel rescue
The workers have been trapped since 12 November – almost two weeks – when a landslide caused a section of a 2.8 mile tunnel being built to collapse some 650ft from the entrance.
Authorities have said the workers are safe, with access to light, oxygen, food, water and medicines via two small tunnels.
Mr Dhami also told reporters: “They are in good spirits. They said, ‘take as many days as you require, don’t worry about us’.”