43-year-old Subash Paul, who climbed the 8,850 meters (29,035 feet) on Saturday, collapsed while descending the Hillary Step ice wall and died the following day. He was among four Indians who lost contact with operators, said Loben Sherpa, a spokesman for Trekking Camp Nepal, which organized their expedition.

Contact was made with Paul and his teammate Sunita Hazra on Sunday, who were helped to descend to Camp 3, but the whereabouts of the remaining two climbers are still unknown. Hiking officials said the chances of finding them alive are slim.

"He (Paul) died while the guides were bringing him down," Sherpa told the news agency Agence France-Presse. "We have sent a helicopter to bring Sunita back," he added.

Up to five deaths

Paul's demise follows the deaths of an Australian woman and a Dutch national since Friday due to altitude sickness in the notorious 'death zone' where the air is so thin that only the fittest can survive without supplementary oxygen.

A rescue team is being organized to retrieve their bodies. Australian university lecturer Maria Strydom died before reaching the summit on Saturday, one day after Dutch climber Eric Ary Arnold perished after attaining the peak.

Favorable weather has allowed nearly 400 climbers to reach the summit from Nepal since May 11, but the altitude, weather and harsh terrain can cause problems at any time.

Everest open again

Trekking companies have been keen to see foreign climbers return to Everest after two years of disasters. Last year, Nepal's devastating earthquake caused the climbing season to be canceled, and climbing attempts were largely abandoned in 2014 after an avalanche above the base camp killed 16 Sherpa guides.

The latest deaths have led to questions about the safety standards of some climbing operators and the preparations made by some climbers.

"Many climbers without any experience crowd Everest every year, and companies often use poor quality equipment... offering cheap packages to clients who are exposed to security risks," Nepal Mountaineering Association Chief Ang Tshering Sherpa said. He urged climbers to pick well-managed companies with experienced guides.

Busier than ever

Some 330 climbers have reached the summit from Nepal since expeditions resumed. Among them was another Dutch climber, Niels van Buren, who suffers from multiple sclerosis. On Friday, the 37-year old became the first person with the diagnosis to scale Everest.

Queues have formed on the final stretch to the summit, which is often secured by a single rope line, leading veterans to complain that slow and inexperienced climbers were holding up others and putting them at undue risk.

Thousands of people have climbed 8,850-meter-high (29,035-foot) mountain since it was first conquered by New Zealander Edmund Hillary and Sherpa Tenzing Norgay in 1953. But more than 250 people have died in the attempt.

mm/kms (AFP, AP, dpa, Reuters)