It took rescuers 17 days – and 400 hours of drilling – to save 41 workers trapped inside a collapsed tunnel in India.

The Silkyara tunnel, connecting various Hindu pilgrim sites throughout the Himalayas, caved in on 12 November.

After more than two weeks of work to save the workers, on Tuesday all 41 men emerged safely.

Here, Sky News looks at how the mission was carried out – and the dangers facing the workers and those trying to retrieve them.

How did they become trapped?

The landslide on 12 November caused the 2.8-mile tunnel to collapse around 650ft (200m) from the entrance, leaving a thick layer of debris in the way.

Authorities were able to pass food and a line of communication to the men through a six-inch (15cm) pipeline, which confined spaces rescue expert Jonathan Davies describes as a “gamechanger”.

He told Sky News: “That was a significant positive step very early on.

“Having that detailed information would mean that the rescue mission could build that into their strategy.

“We knew what [the workers’] status was and if there was any deterioration or any situation that was going to change the rescue strategy.”

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What equipment did rescuers use?

Initially rescue workers used an auger machine to drill horizontally through around three quarters of the 200ft-thick (60m) pile of debris.

Sky’s India reporter Neville Lazarus said “the main obstacle” was “metal meshes that had fallen with the debris and were used in the making of the tunnel”.

“Each time the machine hit that mesh it would crumple its blade and had to be repaired, cut off, and reinserted into the tunnel,” he added.

On Monday, the equipment broke down completely and so-called “rat hole miners” were brought in to drill by hand instead.

“Rat-hole mining” is a banned coal extraction method that was used extensively in India’s northeastern Meghalaya state before it was outlawed in 2014.

It sees miners, often children or short young men, descend ropes or ladders thrown down extremely small holes to extract coal. At least 15 were killed after being trapped in a mine in Meghalaya in January 2019.

Miners began drilling by hand late on Monday after an alternative operation to drill into the tunnel vertically also failed.

Six men worked in two teams of three – with one drilling, the second collecting debris and the third pushing it back through the passageway they had created from welded pipes.

They worked consistently for 24 hours to drill through the remaining 32ft (10m) of rubble.

Mr Davies described the situation as a constant “risk-benefit balance”.

“There was always the risk of potential further collapse and putting the rescuers in danger,” he said.

“On top of that the local geology and remoteness of it added to it. It was a very, very tough situation.”

How did they get them out?

Once the men were in sight, the rescuers used the passage they had created to individually pull the workers out.

It was only 3ft (90cm) wide, however, so each man had to be wheeled through it one at a time on a stretcher.

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Their families, who had been camped out in near-freezing conditions for days, met them as they emerged from the tunnel.

Forty-one ambulances had been put on standby to take each of them to hospital for checks.

Mr Davies said: “There will now be lessons learned and things that can be applied or done better.”

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