The men, low-wage workers from India’s poorest states, have been stuck in the 4.5km in Uttarakhand state since it collapsed on Nov 12.

The process of pulling them out, one at a time on wheeled stretchers through a 90cm-wide pipe, would take a couple of hours, officials said.

The evacuation pipe has to be pushed through and debris cleared before rescue workers can crawl through and begin getting the men out, they said.

Dozens of rescue workers with ropes and ladders were lined up outside the tunnel and ambulances began arriving to take the 41 men to a hospital about 30km away.

The tunnel is part of the US$1.5 billion Char Dham highway, one of Prime Minister Narendra Modi’s most ambitious projects, aimed at connecting four Hindu pilgrimage sites through an 890km network of roads.

Authorities have not said what caused the cave-in but the region is prone to landslides, earthquakes, and floods.