Silkyara/IBNS: Three of 41 men trapped underground in a tunnel in Uttarakhand's Silkyara have been rescued after a 17-day multi-agency rescue operation.

After several high-tech machines failed, the rescuers relied on the banned manual "rat-hole"-mining technique to drill through the nearly 60 metres of rock that threatened to bury the workers.

It will take around two to three hours to rescue all 41 of them.

Three teams of the National Disaster Response Force, or NDRF, are inside the tunnel to bring out the trapped workers.

The India Air Force (IAF) has stationed its Chinook helicopter at Chinyalisaur airstrip in Uttarakhand, about 30 km away from Silkyara tunnel, to airlift workers post their rescue from the tunnel.

The chopper can be used in case any of the rescued workers need urgent medical attention.

The labourers, in such cases, can be airlifted either from the tunnel site to the Chinyalisaur hospital (a distance of 30 km) or flown to the premier All India Institute of Medical Sciences in Rishikesh (a distance of around 160 km).

An emergency medical centre has been set up in Chinyalisaur to treat the 41 workers trapped underground in the Silkyara tunnel since Nov 12.

Forty-one ambulances are on standby at the site of the tunnel collapse, one for each worker, to bring them to the Chinyalisaur hospital by road.

Local police will organise a 'green corridor' to ensure each ambulance reaches the hospital as quickly as possible.

A makeshift medical centre has also been set up - at the mouth of the collapsed tunnel - to provide first aid and emergency care.