The vertical drilling to rescue 41 workers trapped in Uttarkashi's Silkyara tunnel progressed up to 31 metres out of a total of 86 metres.
The drilling work is expected to be completed by November 30.
The option to drill vertically from the top of the hill was chalked out after the auger machine being used for horizontal drilling broke down.
The machine that was stuck in the debris has been cut with a plasma cutter and further drilling will be done manually.
Addressing a press conference in Uttarkashi on Sunday, NHIDCL Managing Director Mahmood Ahmad said, "We have to drill around 86 meters to be done within four days that is by November 30. Hopefully, there will be no further hurdles and the work will be completed on time."
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