KATHMANDU, Nepal — An avalanche that swept a popular Himalayan trekking route has left at least four South Koreans and three Nepali guides missing, the authorities said on Saturday.

The South Korean Ministry of Foreign Affairs said the avalanche hit at an altitude of 10,600 feet before noon on Friday along the popular Annapurna circuit trekking route, which encircles Mount Annapurna in Nepal.

Rescuers plucked 30 trekkers who had been trapped by the avalanche blocking the trail and flew them to safety. An official with Nepal’s Department of Tourism, Meera Acharya, said that at least one Chinese national injured in the avalanche had been rescued by helicopter. Efforts were being made to rescue others.

Weather conditions were poor, with temperature dropping in the past two days, making the operation more difficult.