Rescue operations to evacuate 41 workers trapped in Uttarakhand's Silkyara tunnel resumed on Thursday after an overnight hurdle delayed the drilling by several hours.

Officials were looking at the possibility of the operation ending during the night – provided no more obstacles emerged as an auger machine drilled through the rubble of the collapsed stretch of the tunnel.

Former advisor at the Prime Minister's Office Bhaskar Khulbe, who was at the site, said an iron obstruction that had come in the path of machine drilling an escape path for the workers was removed in the morning.

The setback delayed drilling through the 57-metre stretch of the rubble by six hours, dampening somewhat the previous evening's enthusiasm over the imminent rescue of the workers.

They have been trapped for 11 days after a portion of the under-construction tunnel on Uttarakhand’s Char Dham route collapsed.

At 10 am Thursday, Khulbe told reporters it would take 12 to 14 hours of drilling to insert six-metre sections of steel pipes through the debris.

State government’s nodal officer Neel Neeraj Khairwal told reporters at around 2 pm drilling had progressed by 1.8 metre after the setback Wednesday night at the 45-metre mark.

The entire drilling machine had to be pulled out and realigned, and the iron girder blocking its path cut by experts with the help of the NDRF, he said.

Another officer reported that the 48-metre point had been reached by the drill.

Section-by-section a steel pipe is being pushed through the rubble as the auger machine drills.

Once the chute emerges from the other end, National Disaster Response Force (NDRF) men will enter it to help bring out the trapped workers one by one.

The worker would lie on low-height wheeled stretchers that will be pulled out of the horizontal chute using ropes.

This process is likely to take another three hours, Khulbe said.

The trapped workers are being sent food, medicines and other essentials through a new six-inch wide tube, which is also being used for communication.

Union Minister of State for Road Transport and Highways V K Singh and NDRF Director General Atul Karwal were at Silkyara Thursday to review the rescue effort.

Chief Minister Pushkar Singh Dhami also arrived in Silkyara.

"We have come to around 45 metres. We are very close to you now," he told the trapped workers through the communication system that uses the six-inch wide tube.

The chief minister asked two workers, Gabbar Singh Negi and Saba Ahmad, about the condition of others and praised them for keeping their morale up.

Three scientists from the Central Institute of Mining and Fuel Research, Roorkee, including tunnel expert R D Dwivedi, are also at the site.

International tunnelling expert Arnold Dix said, "It seems we have reached the door and knocking at it. We know people are at the other side of the door." Till 6 pm Wednesday, up to 44 metres of the escape pipe, had been inserted into the debris, according to an official statement.

The drilling of 800 mm diameter pipes from the Silkyara end was earlier put on hold Friday afternoon when the American-made auger machine encountered a hard obstacle around the 22-metre mark, creating vibrations in the tunnel that caused safety concerns.

The drilling resumed around midnight Tuesday and then there was the other, relatively minor, setback the next night.

When the workers come out, they will rushed in ambulances through a ‘green corridor’ under police escort to a 41-bed special ward set up at the community health centre in Chinyalisaur in Uttarkashi district.

If needed, they will then be transferred to other medical facilities.

The NDRF DG said the trapped workers appeared to be in good spirits.

"People who work in tunnels are mentally tough and these people are aware of the huge endeavor being carried out to evacuate them. So they are optimistic," he added.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.