British mountaineer Robin Haynes Fisher, one of the climbers who died on Mount Everest this climbing season, warned of overcrowding at the summit in his last post on social media. On Saturday, Fisher died of what appeared to be altitude sickness at 28,215 feet while descending from the world's tallest mountain.

"I am hopeful to avoid the crowds on summit day and it seems like a number of teams are pushing to summit on the 21st," he wrote in an Instagram post on May 13. "With a single route to the summit, delays caused by overcrowding could prove fatal so I am hopeful my decision to go for the 25th will mean fewer people. Unless of course everyone else plays the same waiting game."

In the post, Fisher shared his condolences for two climbers who died in the "death zone" around 26,000-foot mark in the days leading up to his expedition. 

"Around 100 climbers did summit in those 2 days with sadly 2 deaths, an Indian man found dead in his tent at camp 4 and an Irish climber lost, assumed fallen, on his descent," he wrote, adding that around 700 people were attempting the challenging climb to the peak in the past week and that he planned to delay his own attempt of the summit to May 25 in hopes there would be fewer people.

Everest, which sits on the border of Nepal and Tibet, an autonomous region of southwest China, attracts climbers from around the globe. For this climbing season, which runs from March to May, the Nepalese Tourism Department said it had provided 381 permits to climb Everest as of May 19. A total of 560 people reached the summit of Everest in 2018, Nepal's tourism director Meera Acharya said, according to NBC News.

Congestion at the summit means climbers spend longer than advised in Everest’s "death zone," where oxygen levels are only a third of what they are at sea level. The longer a person spends at the summit, the higher their risk for altitude sickness.

In a statement to BBC, Nepal's tourism authority put the current death toll at eight, although 10 people have been reported dead or missing so far. The department's Director General Dandu Raj Ghimire said overcrowding was not the sole reason for the deaths, other factors including adverse weather conditions had also contributed. In 2018, five climbers died, while six died in both 2017 and 2016. The last year when 10 climbers died in one season was in 2015.

Donald Lynn Cash, a 55-year-old man from Utah, was reported dead Wednesday. Kevin Hynes, 56, from Ireland, died in his tent on Friday and Séamus Lawless, also Irish, was presumed dead after falling near the summit. One Nepalese and four Indians were also dead or missing.

Mount Everest In this photo, unidentified mountaineers walk past the Hillary Step while pushing for the summit of Mount Everest as they climb the south face from Nepal, May 19, 2009. Photo: Getty Images/STR