The operation to rescue 41 workers, who are trapped under the debris caused by a collapsed tunnel in Uttarakhand's Uttarkashi, has reached its final phase, media reports said.

The rescue teams at midnight said about 10 metres of debris is now separating them from the workers who are trapped for 12 days, NDTV reported.

Forty-one ambulances have been kept outside to carry the trapped workers to take to hospital.

Other factors like the difference in temperature between the tunnel and outside, the workers' psychological impact have been kept in mind.

A doctor along with the National Disaster Response Force (NDRF) team will reach the workers and check their conditions once the rescue pipe reaches them.

The workers will walk through the pipe under close supervision of the NDRF, NDTV reported.

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 Brahmakal-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.

On Monday morning, a wider pipe was installed to deliver a wider variety of food and medicine to the trapped people. Earlier, only dry fruits could be sent in.

The rescue ops involved an international tunneling expert team and a robotics team from defence research organization (DRDO).

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

The last rock fall occurred 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.