Authorities in Nepal said it could take up to nearly three weeks to find the four South Koreans who went missing in an avalanche last Friday while trekking near the popular Annapurna Base Camp in northwestern Nepal.

Mira Acharya, a Nepali Tourism Department official, said Sunday seven rescuers from the Trekking Agents' Association of Nepal reached the site with necessary equipment but couldn't begin the search due to new avalanches and rains.

Acharya estimated the search operation could take up to 20 days as the team waits for the weather to clear up.

One of the rescuers said even if the weather clears, it would take several weeks for the snow to melt, hampering the overall operation.

The South Korean government, meanwhile, dispatched an emergency response team to the Nepali capital Kathmandu to assist in the search operations. 

The four school teachers from South Korea's central South Chungcheong Province were trekking with five others on the Deurali part of the Annapurna Base Camp course when the avalanche engulfed them and three Nepali guides.