Rescue teams pulled 20 survivors from the snow that engulfed the road to the Nathu La pass, between Sikkim and the Chinese region of Tibet, before calling off their search as bad weather closed in and darkness fell on Tuesday evening.

“Rescue operations have resumed this morning because we want to make sure that we haven’t left anyone behind. We will scour the area properly before we call them off,” Tenzing Loden Lepcha, a police official in the northeastern state, told Reuters by telephone.

Avalanches have killed at least 120 people in the Indian Himalayas over the past two years.

A study in the US Proceedings of the National Academy of Sciences concluded in 2018 that climate change had increased avalanche risks in the Himalayas.

The cause of Tuesday’s disaster were not immediately clear.

Tourists flock to Sikkim, located below Mount Khangchendzonga, also known as Kanchenjunga, the third highest mountain in the world.

Nathu La serves is a route for the Kailash Mansarovar pilgrimage to Mount Kailash in China, considered one of the holiest pilgrimages in Hinduism.