With the auger machine drilling through the debris of the collapsed Silkyara-Barkot tunnel suffering irreparable damage, authorities on Saturday were looking at alternative plans to evacuate the 41 workers trapped behind the what was nearly 60-metre-thick wall of rubble, in a setback that was poised to delay the rescue operation further.

Officials are now shifting focus to two alternatives — manual drilling through the remaining 10 or 12 metre stretch of the rubble or drilling down 85-90 metres from the top of the mountain.

Briefing mediapersons in Delhi, National Disaster Management Authority (NDMA) member Lt Gen (retd) Syed Ata Hasnain said, “This operation could take a long time.”

READ | Uttarkashi video shows how 41 workers will be pulled out of collapsed tunnel

At the site of the disaster, international tunneling advisor Arnold Dix said the workers will be out “by Christmas”, attributing the delays to a “cautious approach” being followed in the operation.

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 some else take over.

“Only one person who would have to go inside the narrow pipes can be at the forefront. One can’t work for longer in such narrow passage. Shortage of oxygen and heat generated due to the use of machine is another problem,” an RVNL official said on Saturday.

This, officials said, was likely to begin on Sunday, after the rescuers take out the blades of the auger machine that have been stuck inside the evacuation pipes that were being pushed through the debris to create a passage for the men trapped since November 12 to crawl out of.

READ | Uttarakhand tunnel collapse: ‘Auger machine is finished’; official explains delay in rescue

HT on Friday reported that the drilling could not resume after being halted on Thursday afternoon when the platform on which the 25-tonne machine was mounted got destabilised after the drill bit damaged the steel pipes used in the construction of the tunnel. While the machine was disassembled and repaired, officials on Friday said that the evacuation pipe being pushed through the 800mm wide hole being drilled got warped, and the machine was stuck just 10 metres from breaking through.

“It is a big setback for us and could delay the rescue operation for few more days. First we have to try to take out the remaining auger joint from the rescue pipes and have to be cautious at the same time as the process could also damage the pipes that we have inserted through the debris. It could take us back to scratch and all our efforts can go in vain,” the RVNL official cited above said.

An official bulletin on the operation said that the evacuation pipes will be pushed further only after “removal of obstruction”.

READ | Locals bring ‘doli’ of local deity to Uttarkashi tunnel collapse site. Watch

“The pushing for 10th pipe (4.7m length) started at 4.25 pm on November 24, and about 2.2m was inserted by 5.15pm [the same day], resulting in total inserted length of 46.9m. After this an obstruction was observed, and pushing of pipes had to be stopped. Pulling back of Auger started and after pulling back of 15m length of auger, the auger joint got broken. Efforts are ongoing to pull back the rest of 32m auger left inside the pipe. Manual cutting of auger blades has been started inside the pipe to pull out the augers. Further pushing of pipe can only to be taken up after removal of obstruction,” the bulletin said.

A plasma cutter has also been called in from Hyderabad to expedite the operation, Uttarakhand chief minister Pushkar Singh Dhami said, emphasising that the rescue work has been going on in “challenging circumstances”.

“We have removed 20 metres of the [auger] machine by cutting it. We have to remove approximately 25 metres more. We are expecting the machine to be removed completely (from pipes) by Sunday morning. We have also summoned a plasma cutter from Hyderabad and it is expected to reach the tunnel site by night. It will increase the speed of cutting the machine. Currently, we have been able to cut the stuck auger just 1.5m an hour. With the plasma cutter, we can cut the auger at a speed of 4m an hour,” Dhami, who also spoke to the trapped workers, said.

“Once the auger is removed, we will begin manual drilling,” he said.

Secretary, ministry of road, transport and highways, Anurag Jain said, “We have to push through the debris just 10-12 more metres. They will try to complete it as quickly as possible.”

While Dhami did not give a specific timeframe for the operation to end, he said the morale of the trapped men was high.

“I spoke to some of the trapped labourers and everyone’s morale is high. They are not fearful…they (trapped workers) themselves asked us to take them out safely whatever days it takes,” Dhami said, adding that all possible efforts are being made by both the state and central governments.

The workers were seen alive for the first time on Tuesday, peering into the lens of an endoscopic camera sent by rescuers down a thin pipe through which air, food, water and electricity are being delivered.

Though trapped, they have plenty of space in the tunnel, with the area inside 8.5 metres high and stretching about two kilometres in length.

Drilling was at 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, while advising against rushing through the operation.

“If we rush, we can cause another problem…. That is why we are taking our time. We are not going to hurt anybody in the process (rescue). We have been looking at multiple options,” he said.

In an indication that the operation, already in the second week, could stretch further, Dix said, “I have always promised that they will be home by Christmas.”

Heavy equipment, already brought to the site, was being put in place on Saturday for vertical drilling that officials had earlier said could take weeks. Officials said that the machine for vertical drilling by Satluj Vidyut Nigam Limited (SJVNL) has been assembled.

SJVNL will vertically drill 1.2m-wide hole to dig through 85-90m to rescue trapped men from above. This tunnel will be later used for emergency exit, officials had earlier said.

Hasnain indicated that was the quicker of the two main options now being considered, and the process would begin in the “next 24 to 36 hours”, even as CM Dhami said that “work on vertical drilling has begun”.

But the drilling to be undertaken by ONGC will begin only after the report of a field survey in this regard is submitted.

Meanwhile, the work on a platform to use a machine for horizontal drilling from side by Rail Vikas Nigam Limited (RVNL) was underway on Saturday.