LUCKNOW, India (AP) — Rescuers were digging through dirt and parts of a collapsed road tunnel Monday to reach more than 30 workers trapped by a landslide at the construction project in northern India.

All of the construction workers are safe, police officer Prashant Kumar said, adding that they have been supplied with oxygen and water. He said the rescuers had established contact with the trapped individuals.

The collapse occurred Sunday in Uttarakhand, a mountainous state dotted with Hindu temples that attracts many pilgrims and tourists.

Massive construction of buildings and roadways have taken place in recent years in Uttarakhand. The trapped workers were building part of the Chardham all-weather road, a flagship federal government project connecting various Hindu pilgrimage sites.

Kumar said it is not exactly clear how many workers are trapped.

Rescue efforts began Sunday, with authorities pumping oxygen through a pipe into the collapsed section of the tunnel to help workers breathe.

“The team has progressed 15 meters (yards) into the tunnel, with an additional 35 meters (yards) yet to cover,” Kumar said, adding that more than 150 rescuers had used drilling equipment and excavators to clear debris through the night.

The collapsed portion of the 4.5-kilometer (2.7-mile) tunnel is about 200 meters (500 feet) from the entrance, officials told the Press Trust of India news agency.

In January, Uttarakhandstate authorities moved hundreds of people to temporary shelters after a temple collapsed and cracks appeared in over 600 houses because of the sinking of land in and around Joshimath town in the region.