Sherpa guides packed up their tents and left Mount Everest’s base camp on Wednesday in an unprecedented walkout to honour 16 of their colleagues who were killed last week in the deadliest avalanche ever recorded on the mountain, climbers said.

Most attempts to reach Everest’s summit are made in mid-May, when weather is most favourable, but expedition companies already have started cancelling their climbs for the season following Friday’s tragedy. Thirteen bodies were recovered after the avalanche and three Sherpas still missing are presumed dead.

Without Sherpa help, it would be nearly impossible for climbers to scale the mountain anyway. Many climbers will have to forfeit most or all of the money they have spent to go up Everest at a cost of $75,000 or more.

“It is just impossible for many of us to continue climbing while there are three of our friends buried in the snow,” said Dorje Sherpa, an experienced Everest guide.

American climber Ed Marzec said by phone from the base camp that Sherpas were loading their equipment onto a helicopter that had landed at the camp.

“There are a lot of Sherpas leaving this morning, and in the next two days there will be a huge number that will follow,” Mr. Marzec said.

Tusli Gurung, a guide who was at the base camp on Wednesday, estimated that nearly half the Sherpas had already left.

Seattle-based Alpine Ascents International announced it was calling off its expedition. “We have all agreed the best thing is to not continue this season’s climb, so that all can mourn the loss of family, friends and comrades in this unprecedented tragedy,” the company said on its website.

New Zealand-based Adventure Consultants also said it was cancelling its expedition this season.