A member of the National Disaster Management Authority said the rescue could take a long time.
The blades of the auger machine drilling through the rubble of the collapsed Silkyara tunnel were on Saturday stuck in the debris, forcing officials to consider switching to other options that could drag on the rescue of 41 workers trapped inside for 13 days by several weeks more.
Officials are now shifting focus to two alternatives - manual drilling through the remaining 10 or 12 metre stretch of the rubble or drilling down 86 metres from above.
Advising patience, National Disaster Management Authority (NDMA) member Lt Gen (retd) Syed Ata Hasnain said in Delhi "This operation could take a long time." At the disaster site, international tunnelling advisor Arnold Dix repeated his promise of getting the workers out "by Christmas".
Manual drilling would involve individual workers entering the already bored 47-metre stretch of the rescue passage, drilling for a brief period in the confined space and then coming out to let someone else take over.
This, according to Uttarakhand Chief Minister Pushkar Singh Dhami, could begin as soon as the equipment stuck in the planned escape passage is brought out.
Heavy equipment, already brought to the site, was being put in place Saturday for vertical drilling that officials had earlier said could take weeks. The process, Mr Hasnain said, would begin in the "next 24 to 36 hours".
He indicated that was the quicker of the two main options now being considered.
Drilling was at a standstill for almost the entire day Friday, but the extent of the problem was known Saturday when international expert Dix told reporters that the auger machine is "busted".
"Augering is finished... the auger is broken, destructed," he told reporters.
"The mountain has again resisted the auger, so we are rethinking our approach. I am confident that the 41 men are coming home," he said, insisting that they remained safe.
When asked to spell out a timeline, he said, "I have always promised that they will be home by Christmas."
The 25-tonne drilling machine, out of commission for now, includes an auger - a giant corkscrew-like device with a cutter at its end. This has so far created a horizontal passage of 46.8 metres into the rubble out of a total estimated length of 60 metres.
A steel chute had been pushed through, in sections, up to this point, where the rotary blades are stuck, followed by the long auger.
About 20 metres of the auger in the chute has been cut out, Mr Dhami told reporters. A plasma cutter is being airlifted from Hyderabad to tackle the remaining 25 metres.
Once that happens, manual drilling would begin, he said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)