The authorities in Uttarakhand have established communication with workers who are trapped after a portion of an under-construction tunnel collapsed, officials told ANI on Monday.

The tunnel, located on the Brahmakhal-Yamunotri national highway, collapsed in the early hours of Sunday, leaving 40 workers trapped inside. The tunnel is part of the Char Dham Road Project to build all-weather roads in Uttarakhand.

Uttarkashi Circle Officer Prashant Kumar said that all the workers are safe and being supplied with oxygen through a pipe, according to NDTV. The authorities have also sent food and water to them, he added.

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

The Uttarkashi circle officer said that the debris at the spot is about 60 metres deep. “As we are clearing the debris, it is falling from above,” he said. “We have moved around 15 metres inside the tunnel, and 35 metres are still to be covered.”

The National Disaster Response Force’s Assistant Commander Karmaveer Singh Bhandari said the authorities are hoping that by Monday evening, they will breach the debris and reach the site where the workers are trapped, according to ANI. “At that section, the plaster work wasn’t complete, which is why the tunnel collapsed,” he said.

The trapped workers hail from Bihar, Jharkhand, Uttar Pradesh, West Bengal, Odisha, Uttarakhand and Himachal Pradesh, officials said.

Uttarakhand Chief Minister Pushkar Singh Dhami said on Monday morning that he was on his way to inspect the site of the collapse.