A multi-agency operation to rescue 40 people, who are trapped inside an under-construction tunnel in Uttarakhand, are underway, media reports said.

The tunnel on the Brahmakal-Yamunotri National Highway in Uttarakhand's Uttarkashi collapsed in the wee hours on Sunday.

The National Disaster Response Force (NDRF), State Disaster Relief Force (SDRF) and police are conducting the rescue operations.

"Everyone is safe, we are in constant touch with the trapped workers,"  Prashant Kumar, Circle Officer, Uttarkashi said as quoted by NDTV.

Kumar said communication with the trapped workers was established and food and water were supplied.

A narrow opening was earlier made to insert an oxygen pipe in the tunnel and help the trapped labourers.

No casualties have been reported so far.