Rescuers in India are just six or seven metres (20-23 feet) away from 41 men trapped in a collapsed highway tunnel in the Himalayas for more than two weeks, and are confident of drilling through to reach them on Tuesday, officials said.

The men, low-wage workers from India's poorest states, have been stuck in the 4.5 km (3 miles) tunnel in Uttarakhand state since it collapsed on Nov. 12.

So-called rat miners, brought in on Monday to drill through the rocks and gravel by hand after machinery failed, made good progress overnight, officials said.

"About 6 or 7 metres are left," said Deepak Patil, a senior officer leading the rescue, adding that more than 50 metres of an estimated 60 metres of debris had been bored through.

"Sure, 100%," he said when asked if the men could be reached on Tuesday.

The men have been getting food, water, light, oxygen and medicines through a pipe but efforts to dig a tunnel to reach and rescue them with drilling machines have been frustrated by a series of snags.

Rescuers on Monday brought in the "rat miners", experts at a primitive, hazardous and controversial method used mostly to get at coal deposits through narrow passages. Their name comes from their resemblance to burrowing rats.

The tunnel is part of the $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 890- km network of roads.

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