About 30 climbers have suffered frostbite or become ill on Mount Everest after two others died, apparently from altitude sickness.
Two Indian climbers have also been reported missing in the mountain's so-called "death zone" near the summit.
However the mountain's most successful female climber reached the summit for the seventh time on Friday.
Experts say it is not unusual for altitude sickness to claim some lives on Everest.
But this is the first climbing season for two years, after an earthquake in Nepal killed at least 18 people on the mountain last year and 16 guides were killed in an avalanche in 2014, leading to protests that prematurely ended that season.
With the mountain open again, climbers have been taking advantage of good conditions in large numbers, with nearly 400 reaching the summit from the Nepalese side since 11 May.
There have been successful ascents from the Chinese side too, including Lhakpa Sherpa, a Nepalese woman now living permanently in the US and working in a convenience store in Connecticut, who reached the peak from Tibet on Friday — breaking her own record for the most Everest climbs by a woman.
But the weekend's dead and missing have highlighted the dangers of the world's highest mountain.
Dutch climber Eric Ary Arnold died on Friday, after reaching the summit, while on Saturday, 34-year-old Australian woman Maria Strydom also died while descending from the peak. They are the first fatalities of the season.
Indian climbers Paresh Nath and Goutam Ghosh also went missing on Saturday, Wangchu Sherpa from the Trekking Camp Nepal agency in Kathmandu told the Associated Press.
Speaking to the BBC, Gyanendra Shrestha, a Nepalese official at Everest Base Camp, said snow blindness, altitude sickness and fatigue are very common health issues at high altitudes, although most people recover once they descend the mountain.