LUCKNOW, India (AP) — A tunnel under construction at a hydropower project in India’s northern hill state of Uttarakhand collapsed overnight, leaving at least seven workers dead, officials said Friday.

A rescue operation was launched after a sudden rush of water and debris entered the tunnel at the Vishnugad-Pipalkoti hydroelectric project in Chamoli district later Thursday night, said top district official Gaurav Kumar.

Of 22 people who were working in the tunnel, 12 have been rescued alive and another three are still missing, the chief minister of Uttarakhand state Pushkar Singh Dhami told reporters.

Rescue teams from the national and state Disaster Response Force, Indo-Tibetan Border Police and fire services are fighting rising water and debris with as they search for the remaining workers, officials said.

“When our team reached the site and started the operation, there was a lot of water inside the tunnel and water was also seeping from the sides. Since then, the water level has increased considerably,” said the commander of the National Disaster Response Force team, Amrit Lal Meena.

Construction accidents are common in India, where rapid infrastructure growth often collides with fragile geology, construction lapses, extreme weather and safety standards.

In the Himalayan region, fragile mountains, seismic activity and unpredictable underground conditions make tunnel projects especially risky. An explosion inside a coal mine in neighboring Meghalaya state in February killed at least 18 workers. In 2023, a tunnel section in northern Uttarakhand state collapsed, trapping 41 workers for 17 days before they were rescued.