Drilling to prepare an escape passage for 41 workers - trapped at Silkyara tunnel collapse site for a week now - remained suspended on Sunday, while Union Minister Nitin Gadkari who reviewed the rescue operation said another large diameter pipeline was being pushed through the rubble to provide essential supplies to them.

An American auger machine which was brought as a replacement had to be stopped on Friday afternoon after it hit some hard surface while drilling through the rubble in the collapsed part of the under-construction tunnel, following which officials on Saturday began preparations to drill a vertical hole from the top of the hill.

However, Gadkari said horizontal digging seems to be the "best option" and if the auger machine does not encounter any obstacles "it might reach the trapped workers in two-and-a-half days".

The minister said the workers are trapped in an area of the tunnel where they can move around. They have electricity, open space, food, water and oxygen "Saving the trapped workers and evacuating them at the earliest is the biggest priority," the minister, who was accompanied by Uttarakhand Chief Minister Pushkar Singh Dhami, said at a press conference in Silkyara after holding a meeting with experts.

No drilling had begun at the site till Sunday evening but officials said preparations are on to restart the auger machine to bore through the rubble and insert large diametre steel pipes to prepare an escape route for the trapped workers.

"Preparations are underway to restart the auger machine and resume drilling and pipe laying at the tunnel. Apart from one pipe through which food is being supplied to the trapped workers, another large-diameter pipe has also been pushed up to 42 metres to have another lifeline," Disaster Management Secretary Ranjit Kumar Sinha told reporters in Silkyara.

"The Union minister has also suggested that there is space between the top of the debris and the roof of the tunnel which can be explored by robots to see if some pipe for life support can be pushed through it," he said.

Explaining what led to the suspension of the drilling work, Gadkari said it was working alright through soft soil but after it encountered some hard objects it applied more pressure causing vibrations inside the tunnel which posed a danger to the lives of rescue workers.

"Mechanical operation in the Himalayan terrain is challenging as its geological strata is not uniform," he said.

The Union Minister of Road Transport and Highways said if the auger machine works well and hits no major obstacles, horizontal digging through the rubble is the quickest way to reach the trapped workers.

"Though I am no technical expert, in the given circumstances horizontal digging seems the best option. If the auger machine does not encounter any obstacles it might reach the trapped workers in two-and-a-half days," he said.

However, all options including vertical, horizontal, end-to-end and side-to-side drilling options are all being explored because the biggest priority is to evacuate all those trapped at the earliest.

"We are working on six options simultaneously. The PMO is also closely monitoring the operation. Our biggest priority is to save all those who are trapped and as soon as possible. Whatever is needed will be done," he said.

Whichever machine or technical assistance is required will be provided, he said.

"Keeping up the morale of the trapped workers and their family members should be everyone's collective responsibility at the moment," he said.

He said the trapped workers are being constantly provided oxygen, electricity, food, water and medicines.

Road, Transport and Highways Secretary Anurag Jain also said that multivitamins, antidepressants and dry fruits are being provided to the 41 workers trapped for the past seven days.

"Fortunately, there is light inside because the electricity is on. There is a pipeline, and thus water is available. There is a 4-inch pipe, which was used for compression. Through that, we are sending food from day 1," he said.

Jain, in a video update on the rescue operation, said there is water and electricity in the two km portion inside the tunnel, which is the finished part of the 4.531-kilometre two-lane bi-directional tunnel at Silkyara in Uttarkashi.

Experts from different fields have been pooled in and asked to suggest whatever methods can be applied to ensure the safe and early evacuation of the trapped workers, Gadkari said.

Preparations are on to start vertical drilling through the hill above the tunnel, he said, adding every possible method is being tried for their speedy evacuation.

Gadkari said tunnels at a cost of approximately Rs 2.75 lakh crore are being built by the Centre in Jammu and Kashmir, Himachal Pradesh and Uttarakhand.

Many machines have been brought to the site and experts from different government and non-government agencies have been roped in to take their help in the rescue operation.

Another large diameter pipeline of 6 inches has been drilled up to 42 metres through the rubble so that more food like roti, sabzi and rice can be supplied to them.

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