The three climbers were amongst an estimated 150 to reach the 8848m-high summit over the weekend, with the majority ascending on the Saturday.
According to CNN
the three, identified as Eberhard Schaaf, 61, a German medical doctor; Sriya Shah, 33, a Nepali-born Canadian woman; and Song Wondin, a 44-year-old man from South Korea were descending the south slope.
The German doctor Eberhard Schaaf is believed to have suffered high altitude cerebral edema according to Asian Trekking which organized his expedition.
Two other climbers, a Chinese national and his Nepalese Sherpa guide, are reported missing.
According to CNN:
With these three deaths the number of people killed on Everest this year has reached five, ministry official Dipendra Poudel said. Two Nepali sherpas died on the mountain earlier this month.
reports that "first clear weather conditions of the spring climbing season were Friday and Saturday, but a windstorm swept the higher altitudes of the mountain by Saturday afternoon."
They quote Gyanendra Shrestha of Nepal's Mountaineering Department saying: "There was a traffic jam on the mountain on Saturday. Climbers were still heading to the summit as late as 2:30 p.m. which is quite dangerous.
"With the traffic jam, climbers had a longer wait for their chance to go up the trail and spent too much time at higher altitude. Many of them are believed to be carrying limited amount of oxygen not anticipating the extra time spent."
CNN reports that summits from the south side had only commenced on the first safe window period from Friday and that Saturday was windier than usual. On the same day 73-year old Japanese woman, Tamae Watanabe, climbed the mountain from the northern side on the Tibet-China bettering her own record a decade earlier, at age 63, to become the oldest woman to summit Everest.