Officials working to rescue 41 workers trapped inside a tunnel in Silkyara in Uttarakhand for the past 13 days were unable to make any progress through the debris on Friday as the drilling could not resume a day after a metal object in the debris damaged the blades of the machine, people familiar with the operation said.

Drilling still remains to be completed through another 10-12 metres of the debris even after the auger machine has managed to cut through 46.8 metres. Once drilling is complete, evacuation pipes will be installed to bring out the 41 trapped workers.

Senior officials who are part of the evacuation process said that they hope to be able to make contact with the workers on Saturday, if they face no more obstacles.

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On Thursday, drilling was put on hold around 1pm after the platform on which the equipment was mounted got destabilised after the auger machine’s drill bitdamaged the steel pipes used in the construction of the tunnel. Officials said the auger machine had to be disassembled and repaired.

The main problem, officials said, was that the “evacuation pipe” being pushed through the 800mm wide hole being drilled got warped, and the drill machine could no longer cut through.

“The steep pipes had come in the way of the auger machine, and ended up bending the 800mm evacuation pipe we were pushing. The mouth of the other side of pipe ended up getting narrower, and the auger couldn’t push through it. Our team had to chop 1.2m off the pipe which we had pushed into the debris. This process took us around 7-8 hours,” said Neeraj Kharwal, secretary to the Uttarakhand government.

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Since this is at least the fifth time that rescue officials have now faced obstructions in the drilling process, officials said they have now used ground penetration radar (GPR) to scan the remaining debris. “According to the GPR reading, there are no more metallic obstructions in the next 5.4 metres. Its accuracy, however, couldn’t be 100% due to the damage caused to the pipe,” he said.

GPR is a non-invasive geophysical technique that uses radar pulses to image the subsurface, allowing construction workers to detect and map objects and structures beneath the surface of the ground.

Forty-one men have been stranded inside a 2km stretch of the 4.5km Silkyara-Barkot tunnel on the National Highway in Uttarkashi district since November 12, when a portion of the under-construction tunnel collapsed. In the 13 days since, there have been multiple attempts to engineer methods to evacuate the workers, including the use of an American auger machine to drill through close to 60 metres of debris from the Silkyara end.

Till 7.30pm on Wednesday, the rescuers had only 18 metres of the debris left to drill through, when the auger machine hit an iron girder. A team from Trenchless Engineering Services Private Limited (TESPL) entered the pipe twice to confirm the clearance of the rescue pipe. The obstacle was addressed overnight, and drilling restarted at 10am on Thursday.

At 1.30pm on Thursday, as the ninth pipe was pushed through an additional 1.8m, a vibration was noted. Officials then decided to push back the auger to reassess the force to be applied. Then, obstructions were observed again.

“A bent part of forepole (pipe) from the tunnel lining was struck in the auger assembly which led to vibration disturbing the concrete base on which the machine was mounted,” an official said.

“A GPR test was completed at 3.40am on Friday. A team of welders went inside the pipe to cut the bent pipe. The auger reassembly will restart thereafter,” an official release said.

Mahmood Ahmed, additional secretary, ministry of road transport and highways (MoRTH), said the platform has been strengthened and the machine was being re-assembled late on Friday. “Once the welding process of the new pipe is over, which has to be done cautiously and takes two hours, we will start pushing the pipe using the auger machine,” he said, adding that two more pipes of 6 metres are to be pushed before they make contact with the trapped workers.

Bhaskar Khulbe, former adviser to the Prime Minister Office (PMO), said they hoped to reach the workers on Saturday if no more obstacles were faced.

On the other hand, working was also going on several parallel plans to rescue the workers including vertical drilling down the hill to reach them. “The launch pad for the drilling machine has been completed and marking of drilling point over the tunnel has been finalised after discussion with Geological Survey of India (GSI), Rail Vikas Nigam Limited (RVNL) and Oil and Natural Gas Corporation (ONGC),” a government statement said.

The Satluj Jal Vidyut Nigam Limited (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 said.

Meanwhile, Prime Minister Narendra Modi spoke to Uttarakhand chief minister Pushkar Singh Dhami to remain updated about the rescue efforts. The PM also gave necessary instructions to Dhami, a government release said.

Rescue teams said the trapped workers are safe and mentally well. “Freshly cooked food and fresh fruits are being sent to them through a six-inch-wide supply pipe at regular intervals. The consignments consisting of roti, dal, mixed vegetable and fruits like apples, oranges, bananas etc along with medicines and salts are also being supplied to them,” an official familiar of the developments said.

Chaudhary Lal, father of trapped worker Manjeet Lal, said the delayed rescue operation is making him anxious. “Even though they allowed me to speak to my son… the situation remains far from desirable. I wake up every day hoping to be able to see my son. I have already lost my elder son at a Mumbai construction site last year, I don’t want to lose my younger son,” he said.