Most people expect to fight frigid temperatures and fierce winds as they climb Mount Everest.
But a group of three climbers say they faced unexpected adversaries over the weekend while scaling the storied peak: Sherpa guides.
Nepalese authorities say they're investigating reports that a fight broke out on Saturday between the guides and the climbers, nearly 23,000 feet (7,000 meters) up the world's tallest mountain.
"If the Sherpas hit the foreign climbers, action will definitely be taken against them," said Dipendra Poudel, a mountaineering official in Kathmandu.
The fight started after three professional climbers from Italy, the United Kingdom and Switzerland told the Sherpas they wanted to climb on their own, according to Nima Nuru Sherpa of Cho-Oyu Trekking, the agency that is managing their climb.
"Our clients said the Sherpas manhandled them," he said.
A statement posted Sunday on the website of Italian climber Simone Moro gave a harrowing account, claiming that 100 Sherpas attacked him, Swiss climber Ueli Steck and British climber Jonathan Griffith.
This account said the fight broke out after Sherpas said the climbers knocked ice onto a Sherpa located below them.
"They became instantly aggressive," the statement said, "and not only punched and kicked the climbers, but threw many rocks as well."
After nearly an hour, the situation calmed down, the statement said.
"The climbers, who had been pushed away and told to hide, had regrouped and were told that if they weren't gone in one hour that they would all be killed," the statement said.
"The climbers packed the bare essentials and made a circuitous route back down to the base of Mount Everest in heavily crevassed terrain with no rope on, feeling that given the current situation this was the safest place to be."
Nepalese authorities said their investigation into the report was ongoing.
"The Sherpas got angry when hit by the ice and there was a fight," said Dambar Parajuli of the Expedition Operators' Association, a group representing expedition organizers.
In addition, he said, the climbers had been instructed not to go up while Sherpas were laying ropes, but they went ahead despite the warning.
On Monday, he said, both sides had a meeting, reconciled and agreed to go ahead with the climb.
In their statement on Sunday, the climbers said no Sherpa had come forward with any evidence of injury.
"The climbers believe that the lead Sherpa was tired and cold and felt that his pride had been damaged as the three climbers were moving unroped and much faster to the side of him," the statement said. "Whatever the reason may be, there is no reason to instigate vigilante rule and to try and kill three visiting climbers."
About 4,000 people have scaled Everest since Sir Edmund Hillary and Sherpa Tenzing Norgay first climbed the mountain in 1953.
According to mountaineering officials, 340 foreign climbers from about 30 expeditions have been given permission to climb Everest this year with about the same number of high-altitude Sherpas set to assist them.