The auger machine engaged for drilling through the rubble at the Silkyara tunnel to rescue 41 trapped workers has busted, international tunnelling expert Arnold Dix said on Saturday.

"Augering is finished...the auger is broken, destructed," he told reporters in Silkyara.

The auger machine was facing repeated obstructions in the rubble in the past few days.

When asked about other options such as vertical or manual drilling, he said all options are being explored.

"Every door we are opening has its advantages and disadvantages. What we have to ensure is the safety of the rescuers as well as those who are trapped," he said.

The multi-agency rescue effort began November 12 when a portion of the under-construction tunnel on Uttarakhand's Char Dham route collapsed following a landslide, trapping the 41 workers inside.

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