Indian rescuers drilled through rocks and debris on Tuesday to reach 41 workers trapped for 17 days in a collapsed tunnel in the Himalayas, and are set to pull them out one by one to safety, officials said.

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

The process of pulling them out, one at a time on wheeled stretchers through a pipe that's 90cm in diameter, will 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 30 kilometers away.

The tunnel is part of the $1.5 billion Char Dham highway, one of Indian 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.

(Cover: Rescue personnel work at the collapsed tunnel in the Uttarkashi district of India's Uttarakhand state, November 28, 2023. /CFP)