Working overnight with a powerful machine, rescue workers had by Friday morning drilled up to 21 metres through the rubble in Silkyara tunnel, inching closer to the 40 labourers trapped there for five days.

The workers need to drill up to 60 metres to insert 800 mm and 900 mm diameter pipes – one after the other -- with the help of a giant drill machine till an escape passage is created for the labourers stuck behind the collapsed portion of the under-construction tunnel, NHIDCL Director Anshu Manish Khalkho said.

The labourers have been trapped since Sunday morning when a part of the tunnel collapsed following a landslide.

"Drilling has been done up to 21 metres so far," the state emergency operation centre's control room in Silkyara said.

The stretch where debris is accumulated begins 270 metres from the mouth of the tunnel at Silkyara side.

Uttarkashi District Magistrate Abhishek Ruhela said that the trapped workers are safe and being supplied with oxygen, medicines, and food and water through pipes.

Constant communication is being maintained with them to keep up their morale, he said.

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