Three climbers have died on their descent from the summit of Mount Everest, tour agents and officials said Monday, bringing the season's death toll to five on the world's highest peak. A 61-year-old German and a South Korean aged 44 died on the mountain's south face on Sunday, Ang Tshering Sherpa of the Kathmandu-based Asian Trekking adventure agency said. "We are sad to announce the death of Eberhard Schaaf, of Germany, at the south side of the summit of Mount Everest," Sherpa told AFP. "The medical staff at the Himalayan Rescue Association believe the cause of death to be altitude sickness." Sherpa said South Korean Song Won-Bin, who had been missing since Saturday, died at "The Balcony", an area near the top of the 8,848-metre (29,029-feet) peak. Tilak Pandey, a tourism ministry official at the Everest base camp, told AFP separately that a Nepali-born Canadian woman named Shriya Shah had also been killed on Sunday. "Most of these deaths occur due to high altitude sickness," said Sherpa. "Climbers spend their energy on the ascent and they are exhausted and fatigued on the descent." He added that a Chinese climber and a Nepali mountain guide were also missing. Two Nepali Sherpa climbers died on Everest in April, one falling into a crevasse at 5,900 metres and the other succumbing to altitude sickness at the base camp.