Around 40 workers are still trapped in a tunnel in Uttarakhand for about 150 hours, with a massive drill being utilised for their rescue.

The rescue efforts were interrupted last evening due to a sudden "cracking sound" and a malfunction in the drilling machinery.

Authorities announced plans to airlift a second large drill to the site of the accident, with rescue op likely to restart by 10 am.

Forty workers have been trapped since Sunday morning following a collapse in part of the tunnel.

According to the officials, the workers are safe and are receiving food and water through steel pipes inserted into the tunnel's opening.

Relatives of the trapped workers have gathered at the site. A brother of one of the workers expressed urgency for a swift rescue before their health deteriorates.

Medical professionals have stressed the importance of thorough rehabilitation for the workers due to concern about the mental and physical impacts of their extended entrapment.

The collapse of a section of the Silkyara Tunnel under construction on 12 November led to 40 construction workers being trapped under debris.

Rescue attempts have been hampered by falling debris during drilling as rescuers try to create a space to push through pipes for the men to crawl to safety.

Drilling activities were suspended on Friday evening following the detection of a significant "cracking sound."

The Air Force has transported a second drilling machine from Indore using a C-130 Hercules military aircraft.