At least four climbers were found dead inside their tents on Mount Everest at a high altitude camp, Reuters reported on Wednesday. With this, the toll on Mount Everest this climbing season has reached 10.

A group of sherpas found the bodies inside two tents located at 8,000 metres at Camp 4, Mingma Sherpa of the Seven Summit Treks group told the news agency in Kathmandu, Nepal. Two of the deceased were Nepali and the other two were foreigners, The Himalayan Times reported, quoting unidentified officials. The sherpas were at Camp 4 to locate the body of Slovak mountaineer Vladimir Strba who had died on Sunday trying to scale the mountain.

The sherpas believe the climbers might have died of suffocation inside the tents. Strba’s body was being bought to Camp 2 from Camp 4, they said.

On Monday, the sherpas had found Indian climber Ravi Kumar’s body on Mount Everest. The 27-year-old is believed to have fallen on his way down after reaching the summit on Saturday. An American doctor, Roland Yearwood had died of altitude sickness on Sunday.

In April, Swiss climber Ueli Steck died while he was on an acclimatisation climb and 85-year-old Min Bahadur Sherchan died in May while trying to reclaim his title as the world’s oldest person to summit Everest.