SILKYARA TUNNEL, India - Ambulances were on standby Thursday as Indian rescuers dug through the final metres of debris separating them from 41 workers trapped in a collapsed road tunnel for nearly two weeks.

Rescue teams have specially fitted stretchers with wheels, ready to pull the exhausted men out through 57 metres (187 feet) of steel pipe -- once it is driven through the final section of the tonnes of earth, concrete and rubble blocking their escape.

Emergency vehicles and a field hospital stood ready, preparing to receive the men who have been trapped since a portion of the under-construction tunnel in the Himalayan state of Uttarakhand caved in 12 days ago.

"We have done rehearsals on how to get people safely out," National Disaster Response Force chief Atul Karwal told reporters Thursday.

"The boys will go in first," he said. "We have put wheels under the stretchers so that when we go in, we can get the people out one by one on the stretcher -- we are prepared in every way."

But rescue efforts have been hit with repeated delays, including more debris falling, fears of further cave-ins and drilling machine breakdowns, as progress on Thursday was slowed by further mechanical problems.

'Himalayan geology is the enemy' 

"The 10 to 12 metres (32 to 39 feet) remaining... we don't know what can come up, but we are ready to handle it," Karwal said, adding that the trapped men were "keeping up their morale".

Uttarakhand chief minister Pushkar Singh Dhami said the work was on a "war footing", with a "team of doctors, ambulances, helicopters and a field hospital" set up.

Syed Ata Hasnain, a senior National Disaster Management Authority official, refused to say when the men might be freed.

"This is like battle," the retired general told reporters. "You cannot put a timeline on it. In battle, you don't know what the enemy is going to do.

"Here, the land is your enemy. Himalayan geology is the enemy... it is very challenging work."

Experts have warned about the impact of extensive construction in Uttarakhand, large parts of which are prone to landslides.

"The rescuers and the workers stuck inside are at equal risk," Hasnain added.

Arnold Dix, president of the International Tunnelling and Underground Space Association, told AFP while it was "not nice" the men were trapped, that fact they were safe was a "gift."

"Normally when I am responding to a rescue, there is some flooding or we're running out of oxygen or something terrible is happening," he said, noting the areas where the men were was stable.

Prayers for safe release 

The area was a flurry of activity with worried relatives gathered outside the site, where a Hindu shrine has been erected, with a priest holding prayers for the safe rescue of the trapped men.

"The day they will come out of the tunnel, it will be the biggest, happiest day for us," said Chanchal Singh Bisht, 35, whose 24-year-old cousin Pushkar Singh Ary is trapped inside.

In case the route through the main tunnel entrance does not work, rescuers also started blasting and drilling from the far end of the unfinished tunnel, nearly half a kilometre (over a quarter of a mile) long.

Preparations have also been made for a risky vertical shaft directly above.

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.

Though trapped, they have plenty of space, with the area inside 8.5 metres high and stretching about two kilometres in length.

The tunnel is part of Prime Minister Narendra Modi's infrastructure project aimed at cutting travel times between some of the most popular Hindu sites in the country, as well as improving access to strategic areas bordering rival China.