The death toll in Friday’s avalanche at Mount Everest, the world’s highest peak, has risen to at least 13. Rescuers recovered the 13th body on Saturday.

The avalanche struck Friday morning, while a group of Nepalese Sherpas were setting up a rope along a climbing route. According to Reuters, the avalanche hit in a dangerous area called Khumbu Icefall, where ice frequently breaks without any warning.

“We were tied on a rope and carrying gas to camp when there was a sudden hrrrr sound,” Ang Kami Sherpa, 25, one of the survivors flown to a Kathmandu, told Reuters. “We knew it was an avalanche but we couldn't run away or do anything.”

The Telegraph reposts that Sherpas used helicopters in their rescue efforts, trying to find other survivors before weather conditions grew worse.

International climbers had been gathering at Base Camp as the climbing season is set to start. However, they have decided to hold off plans for four days. Some have even decided to cancel their plans all together.

“Everyone is shaken here at Base Camp. Some climbers are packing up and calling it quits, they want nothing to do with this,” Tim Rippel of Peak Freaks Expeditions wrote on his blog.

An NBC News crew was at the mountain to film a documentary for a Discovery Channel stunt, the future of which is still in question. Universal also had a crew there working on the Jake Gyllenhaal film Everest, and they are safe as well. The main actors were not working on the film at the time.

The avalanche is the single worst disaster in recorded history at the mountain.