Ambulances were on standby and a special ward at a local health centre kept ready as a multi-agency effort to rescue 41 men trapped in the Silkyara tunnel appeared close to success on Wednesday evening.

In a late evening development, drilling of steel pipes through the rubble hit a hurdle when some iron rods came in the way of the auger machine. Officials, however, expected the rescue mission to be over by early Thursday morning.

Till 6 pm, up to 44 metres of an escape pipe had been inserted into the debris of the collapsed stretch of the tunnel in Uttarakhand's Uttarkashi district, an official update said in Delhi.

Earlier, officials said the American-made auger machine had to drill through a 57-metre stretch of debris to reach the workers, who were trapped when a portion of the under-construction tunnel collapsed 10 days back.

By this count, just 13 metres of debris remained to be drilled through.

As the drilling of 800 mm diameter steel pipes through the rubble hit a hurdle on Wednesday evening, an official said, "It is a minor hurdle which NDRF personnel have started cutting." "It will take them one-and-a-half hours at the most to remove them from the way before drilling starts again," said the project head of Jozila Tunnel who is lending a helping hand in the rescue operations in Silkyara.

Two more pipes of six metres each are to be laid through the rubble to complete the escape passage for the trapped workers, he said.

Asked how much time it is going to take to complete the exercise, the official said cutting iron rods will not take more than one and a half hours but laying two more pipes and welding them together might take some more time.

In any case, the mission might end by 8 am on Thursday, he said.

Drilling from the Silkyara end was put on hold Friday afternoon when the 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.

As the machine drills through, six-metre sections of steel pipes, just under a metre wide, are pushed into the escape passage. Once the pipeway reaches the other end, the trapped workers are expected to crawl out.

A National Disaster Response Force (NDRF) team was spotted entering the tunnel in the evening.

A team of 15 doctors, including chest specialists, has been deployed at the site in anticipation of the evacuation. Twelve ambulances were on standby at the spot, and the plan was to keep a fleet of 40 ready.

A helicopter was also expected to be earmarked for the operation. A special ward to accommodate all evacuated workers was readied at the community health centre in Chinyalisaur. All hospitals in the district as well as AIIMS, Rishikesh are on alert, officials said.

Relatives of workers who have spoken to them through a new six-inch pipeline inserted late Monday through the rubble expressed optimism.

"Today, we were taken inside the tunnel and we spoke to our family member. Sonu repeatedly told me not to worry now and that we would meet soon," Devashish, whose brother-in-law is among the 41 workers, said.

"We called him on Diwali but could not reach him. His colleagues told us that his mobile phone was damaged. Later, we saw his name in the newspaper and learnt that he was trapped inside the tunnel," he said.

At a media briefing in Silkyara around 4 pm, Bhaskar Khulbe, a former advisor with the Prime Minister's Office, was upbeat, saying that another six-metre section of the rescue pipe had been inserted over the past hour.

"Hopefully, the next two to three hours will be comfortable in terms of assembling for the next push and attaining what all of us are waiting for," he said.

Officials had said earlier that the stretch between 40 and 50 metres was the "most crucial" one.

Asked to spell out a timeline for workers' evacuation, Khulbe had said, "We hope to celebrate Bagwal with them", possibly meaning Igas, a festival celebrated in the Garhwal region after Diwali.

This year Igas will be celebrated on Thursday.

Several alternative plans are also in motion if the horizontal drilling from the Silkyara end fails.

Officials said about nine metres of horizontal drilling had taken place from the Barkot end of the tunnel - a much longer process that could take several days.

Prime Minister Narendra Modi spoke to Chief Minister Pushkar Singh Dhami once again on Wednesday morning for updates on the rescue operation.

First visuals of the trapped workers were captured early Tuesday with the help of an endoscopic camera sent through the new six-inch pipeline.

In a statement, the government said the second lifeline was functioning efficiently, ensuring an ample supply of food items like rotis, sabzi, khichdi, daliya, oranges, and bananas in the tunnel.

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