SILKYARA TUNNEL, India, Nov 25, 2023 (BSS/AFP) - Indian rescuers brought in a new digging machine Saturday to open a vertical shaft to free 41 workers trapped inside a collapsed road tunnel for two weeks, after efforts through another route hit snags just metres from reaching the men.

In the latest setback in frantic attempts to rescue the increasingly desperate workers, engineers driving a metal pipe through 57 metres (187 feet) of rock and concrete ran into metal rods and construction vehicles buried in the earth.

Just nine metres (30 feet) from breaking through, drilling with a giant earth-boring machine has stalled, while using gas cutting tools to remove thick metal girders from inside the confined pipe -- just wide enough for a man to crawl through -- is tricky.

"Work is now being done to cut and clear the blockage," top local civil servant Abhishek Ruhela told AFP on Saturday.

After the massive drill stopped, rescuers attempting to reach the men through the blocked main tunnel entrance are now working to clear the route without it, rescue officials said.

Rescue efforts have been painfully slow, complicated by falling debris as well as repeated breakdowns of crucial heavy drilling machines, with the air force having to twice airlift in new kit.

Ambulances are on standby and a field hospital has been prepared to receive the men, who have been trapped since a portion of the under-construction Silkyara tunnel in the northern state of Uttarakhand caved in on November 12.

- 'Challenging Himalayan terrain' -

At the same time, AFP reporters at the site saw a heavy earth digger being taken up the specially cut track to the top of forested hill above the tunnel to start a risky vertical shaft.

"The work of reaching the labourers trapped inside is in the final stages," Ruhela told AFP. "Whatever option possible to reach them is being considered."

Officials estimate the proposed vertical shaft would need to be 89 metres (291 feet) deep, a complex dig above the men in an area that has already suffered a collapse.

Work has also begun digging from the far side of the road tunnel, a much longer third route estimated to be around 480 metres.

Rescue teams have stretchers fitted with wheels ready to pull the exhausted men through 57 metres of pipe, if it can be driven through the final section of rubble blocking their escape.

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.

Since Wednesday, officials have repeatedly said they were optimistic of a breakthrough within hours, but a government statement has also noted that any timeline is "subject to change due to technical glitches, the challenging Himalayan terrain, and unforeseen emergencies".

- 'Very careful in further progress' -

Syed Ata Hasnain, a senior rescue official and retired general, said their efforts were "like battle".

"By any means, we must get these brave men out," he told reporters on Friday afternoon, adding that "all resources" needed were being utilised.

"This is a war that is being fought to save the sons of India who have been toiling up there in the mountains," Hasnain said, adding that the final stretch was critical.

"We are going to be very, very careful in further progress," he said.

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.

The area outside has been a flurry of activity, with worried relatives gathering and rescue teams praying at a Hindu shrine erected at the entrance.