The rescuers have drilled about halfway through the debris where 41 workers are still trapped following the collapse of a tunnel in Uttarakhand's Uttarkashi for 11 days, media reports said.

The rescue workers have drilled 32 out of 60 metres that need to be cleared for the workers to come out.

The Centre has come up with a five-option action plan that involves drilling from three sides to access the trapped workers.  Five different agencies have been tasked with carrying out each operation.

Two tunnels will be drilled horizontally from the right and left sides of the main tunnel, while a vertical shaft will be drilled from the top of the tunnel.

The labourers have been trapped in a 400-metre buffer zone of the unfinished main tunnel since November 12 when a portion of the 4.5-km tunnel on the Brahmakhal-Yamunotri National Highway collapsed, trapping 41 workers.

The tunnel - meant to join Silkyara and Dandalgaon in Uttarkashi - is a part of the Char Dham project.

However, the big challenge is finding space for the multiple drilling machines needed in the hilly terrain and the time-consuming job of building motorable roads, which has already started.

At present, a single machine is operating in the area, clearing the way for a heavier machine. Workers are building a ramp from the main tunnel's entrance to its roof to transport the heavier machines.

On Monday morning, a wider pipe was brought and is currently being installed. This will allow rescuers to deliver a wider variety of food and medicine to the trapped people.

Earlier, only dry fruits could be sent in. With the new pipe, the authorities will be able to provide more substantial meals.

An international tunnelling expert team arrived at the spot and the International Tunnelling and Underground Space Association president Arnold Dix is overseeing the operations.

A robotics team from defence research organization DRDO has also reached.

Over the last week, several plans to cut through the 40-meter rock wall fell through.

The last rock fall took place on Friday when attempts were made to use an American Auger drill flown in from Delhi. The drill machine that was being used before that had broken down and work had to be stopped till the new one reached.