Indian rescuers are considering opening a vertical shaft to free 41 men trapped in a collapsed tunnel after drilling at the site was paused over fears of further cave-ins and as efforts stretched into a second week.

Excavators have been removing earth, concrete and rubble from the under-construction tunnel in the Northern Himalayan state of Uttarakhand since last Sunday after a portion of the tunnel collapsed.

Rescue efforts have been slowed by continued falling debris as well as repeated breakdowns of the crucial heavy drilling machines, with the air force having to twice airlift in new kit.

Drilling through the tones of debris was halted late Friday, after a cracking sound created a "panic situation".

Relatives of those trapped, who spoke to the men via radio, said conditions were grim and morale low.