Manual horizontal drilling has started at the Uttarakhand tunnel where 41 men have been trapped for more than two weeks, reports said.

The process started this evening after the American Augur Drill broke again, its blades fouled up by an iron grill from the tunnel ceiling and other debris.

The work is being conducted by "rat miners"—labourers used to drill narrow shafts as part of a primitive method of coal extraction.

The vertical drilling to create an extra passageway has already progressed to 36 meters, officials said.

Manual drilling from top and side are the two methods on which rescue workers are focussing after several other methods failed. Horizontal drilling from the Barkot end of the tunnel is also in progress.

Neeraj Khairwal, Secretary, Uttarakhand government, said 24 rat miners will work 24 hours to remove manual debris. The work will be done in three shifts.

The Auger Machine, once in working condition, will push the 800-mm pipe forward as the manual drilling progresses.

The officials, however, refused to give a time frame for the rescue.

Manual drilling is a slow and labor-intensive process in which the rat-hole miners will go through the 800 mm pipe, drill manually, and bring out the debris with shovels.

With 10 to 12 meters left to reach the trapped workers and machine drilling options exhausted, manual drilling appears to be the only way forward, the authorities indicated.