Indian rescuers have been battling to free 41 men trapped in a road tunnel for nine days as they prepared to dig an entirely new shaft after previous efforts failed.

Excavators have been removing earth, concrete and rubble from the under-construction tunnel in the northern Himalayan state of Uttarakhand since 12 November after a portion of the tunnel collapsed.

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

Engineers had been trying to horizontally drive a steel pipe through the debris, just wide enough for the increasingly desperate men to squeeze through.

However, drilling on that route was paused on Friday, after a cracking sound created a "panic situation", officials said.

Teams were now preparing to dig the new shaft from above, forcing workers to cut an entirely new track up to the top of the forested hill high above for the heavy equipment needed.

A portion of the tunnel collapsed on 12 November

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

"Every effort is being made," Uttarakhand chief minister Pushkar Singh Dhami said in a statement today, insisting that the "workers trapped in the tunnel are safe".

He said he had spoken to Prime Minister Narendra Modi about the crisis.

Top local civil servant Abhishek Ruhela said the track to the new drilling site was three-quarters built.

"Up to 900 metres of the 1,200 metre-long road being built for drilling over the tunnel has been completed," Mr Ruhela told AFP.

Excavators have been removing earth, concrete and rubble from the under-construction tunnel

Rescuers have been communicating with the trapped workers by radio, while food, water, oxygen and medicine have also been sent to them via narrow pipe, with workers planning to expand that to allow bigger food packets to be sent.

Foreign experts have been drafted in, including independent disaster investigator Arnold Dix, president of the International Tunnelling and Underground Space Association.

"We are going to find a solution and get them out," Mr Dix told reporters at the site today.

"A lot of work is being done here. It is important that not only the men rescued but also the men who are (doing the) rescuing are safe," he added.

Villagers have set up a Hindu temple at the mouth of the tunnel to the local god Boukhnag saying the original temple had been moved during construction.

Some villagers blamed the tunnel collapse on the fact that the initial temple was destroyed.

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