An American climber died while descending Mount Everest on Monday, bringing this years death toll on the mountains Nepali side to at least nine amid concerns of overcrowding on the summit.

A Nepalese official said Monday morning that 61-year-old Christopher John Kulish ascended the more than 29,000-foot peak by taking its Southeast Ridge route, but died suddenly while coming down, Reuters reported .

The cause of death remains unknown.

On Saturday, 44-year-old British climber Robin Haynes Fisher died in the mountains death zone, an area infamous for its low oxygen levels due to its altitude.

He was descending with his sherpa guides from the summit when he suddenly fainted, Murari Sharma, an employee of the Everest Parivar Treks expedition company that organized Fishers trip, said of the climber.

An Instagram post flagged by CNN shows that on May 19, days before his death, Fisher wrote that he was hopeful to avoid the crowds on summit day and it seems like a number of teams are pushing to summit on the 21st.