All 40 workers trapped after an under-construction tunnel collapsed in Uttarkashi are safe and communication has been established with them, officials said on Monday as Chief Minister Pushkar Singh Dhami reached the site to oversee rescue operations.

Rescuers who worked overnight trying to prepare an escape passage for the labourers have provided them with food and water, the Silkyara police control room said.

A portion of the tunnel being built between Silkyara and Dandalgaon on the Brahmakhal-Yamunotri National Highway caved in on Sunday morning.

According to the District Emergency Operation Centre, the labourers trapped inside the tunnel for over 24 hours now are from Bihar, Jharkhand, Uttar Pradesh, West Bengal, Odisha, Uttarakhand and Himachal Pradesh.

The officials said attempts were being made to stabilise the constantly falling loose debris. A nearly 30-metre stretch of the tunnel, being built by the National Highways & Infrastructure Development Corporation Limited (NHIDCL), has been affected by the cave-in.

NHIDCL Director Anshu Manish Khalko said loose debris hampering the rescue efforts was being stabilised using shotcrete – a process involving spraying concrete.

Rescue efforts by personnel from multiple agencies, including the National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), Indo-Tibetan Border Police (ITBP) and the Border Roads Organisation (BRO), have been going on since Sunday morning.

Khalko said, "All the trapped labourers are safe. They have been contacted several times on walkie-talkie and edibles and drinking water have been supplied to them.

District Magistrate Abhishek Ruhela went inside the tunnel on Monday morning to review the rescue efforts and discuss the strategy to save the labourers.

Dhami was accompanied by Garhwal Commissioner Vinay Shankar Pandey as he arrived in Silkyara to assess the situation.

The officials are optimistic about the safety of the trapped labourers as enough oxygen was made available to them through a water pipeline.