Indian officials have repeatedly promised 41 men trapped in a collapsed Himalayan tunnel for more than two weeks will be safe, but desperate relatives say they are pinning hopes on prayer.

Our only source of strength is God, as it is the last hope for us, said mother-of-three Musarrat Jahan, whose husband Mohd Sabah Ahmad is a migrant worker trapped behind the tonnes of rubble, concrete and earth in the bitterly cold mountain air.

We have more faith in God than anything, she said, speaking by phone from her home in the eastern state of Bihar, one of Indias poorest.

Most of the trapped men are migrant workers who left home to find employment, working on the Silkyara tunnel in northern Uttarakhand state, more than 870 kilometres (540 miles) away from Bihar state in the forested Himalayan foothills.

Jahan said she had spoken to her husband via a telephone exchange set up inside the tunnel with the help of her brother-in-law, who has been camping at the site since shortly after the accident on November 12.

My husband assured me that he is safe and hopeful to come out soon, she said.

Rescue operations have been hit by repeated setbacks, including fears of further debris falling and the repeated breakdown of drilling machines snarled up by hitting metal girders trapped in the rubble.

On Monday, military engineers began digging the final stretch by hand.

˜Sleepless nights

Guriya Devi has not stopped crying for her husband, 31-year-old Sushil Kumar.

Devi said she has been glued to her phone, searching for new updates as the rescue stretched into its third week.

We are crying and going through sleepless nights¦ But we are still hopeful that rescuers will succeed in their operation she said.

The workers were seen alive for the first time last week, peering into the lens of an endoscopic camera sent by rescuers down a thin pipe through which air, food and water are being delivered.

Authorities say the men are healthy and safe.

Abhishek Kumar, whose older brother Sonu Shah is among the trapped, said he cannot wait for the day he gets word he is free.

˜Problems are increasing

But the delay in getting good news has been traumatic, he told AFP by phone from his home in Bihars Saran district.

Our wait is growing and our patience is stretching, he said.

We are now waiting for the end result, he said. If the end is good, everything will be fine.

The rescue operations have been an ordeal for the family members, with no imminent end in sight.

Kumar said it was a matter of serious concern that the efforts have not been successful.

It appears difficulties and problems are increasing to safely rescue them, he said.

He said his family had their hopes dashed already after officials said they were hopeful of being hours away from a breakthrough, only for that to turn to delays of days.

Uttarakhand chief minister Pushkar Singh Dhami has vowed all the men would be rescued.

Do not worry, all the labourers will be taken out safely, he said.(AFP)

Principal Secretary to the Prime Minister of India, Pramod Kumar Mishra (6L) reviewing the rescue of workers trapped beneath the collapsed under construction Silkyara tunnel