At least 36 workers were trapped after a portion of an under-construction tunnel on the Brahmakhal-Yamunotri national highway in Uttarakhand collapsed in the early hours of Sunday.

No casualties have been reported so far.

The incident took place at around 4 am between Silkyara and Dandalgaon villages in the state’s Uttarkashi district, PTI reported.

The National Disaster Response Force, the State Disaster Response Force, the police and the fire brigade are conducting rescue operations.

“As per the records [of the National Highways and Infrastructure Development Corporation], 36 workers are trapped inside,” Uttarkashi Superintendent of Police Arpan Yaduvanshi told reporters. “Rescue operations are under way on war-footing. We will rescue all of them safely.”

Employees of the National Highways and Infrastructure Development Corporation, the organisation constructing the tunnel, were also present at the spot.

Uttarakhand Chief Minister Pushkar Singh Dhami told news agency ANI that he was in contact with officials about the incident.