On the northern Tibet side of the mountain, a 56-year-old Irish man died on Friday morning, his expedition organisers confirmed in a statement on their Facebook page.

The man decided to return without reaching the summit but died in his tent at the North Col pass at 7,000 metres (22,965 feet).

Four climbers from India and one each from the United States, Austria and Nepal have already died on Everest in the past week. Another Irish mountaineer is missing presumed dead after he slipped and fell close to the summit.

A traffic jam of climbers in the Everest “death zone” has been blamed for at least four of the deaths, heightening concerns that the drive for profits is trumping safety.

Nepal issued a record 381 permits for mainly foreign climbers, costing US$11,000 each, for the spring climbing season.

Each climber with a permit is assisted by at least one sherpa, adding to the summit logjam.

With the short window of suitable weather set to close soon, bottlenecks of scores of climbers wanting to achieve the ultimate mountaineering accolade have built up each day.

An estimated 600 people had reached the summit via the Nepal side by Friday, a government official said, based on information from expedition organisers.

At least 140 others have been granted permits to scale Everest from the northern flank in Tibet, according to operators. This could take the total past last year’s record of 807 people reaching the summit.

Many Himalayan mountains – including Everest – are at peak climbing season, with the good weather between late April and the end of May. Eight other climbers have died on other 8,000-metre-plus Himalayan peaks this season, while two are missing.

Ang Tsering Sherpa, former president of the Nepal Mountaineering Association, said that the weather window to summit this season was narrow, meaning that many teams had to wait to go up.

“Spending a long time above the death zone increases the risk of frostbite, altitude sickness and even death,” he said.

Kalpana Das, 52, reached the summit but died on Thursday afternoon while descending, as a huge number of climbers queued near the top. The other Indian, Nihal Bagwan, 27, also died on his way back from the summit.

“He was stuck in the traffic for more than 12 hours and was exhausted. Sherpa guides carried him down to Camp Four but he breathed his last there,” Keshav Paudel of Peak Promotion said.

A 33-year-old Nepali guide died at the base camp on Friday after he was rescued from Camp Three for falling sick.

Wednesday claimed the lives of an American and another Indian. Donald Lynn Cash, 55, collapsed at the summit as he was taking photographs, while Anjali Kulkarni, also 55, died while descending after reaching the top.

Kulkarni’s expedition organiser, Arun Treks, said heavy traffic at the summit had delayed her descent and caused the tragedy.

“She had to wait for a long time to reach the summit and descend,” Thupden Sherpa said. “She couldn’t move down on her own and died as Sherpa guides brought her down.”

Pasang Tenje Sherpa, of Pioneer Adventure, said Cash collapsed on the summit and died close to Hillary Step as guides were bringing him back.

Last week, an Indian climber died and an Irish mountaineer went missing after he slipped and fell close to the summit and is presumed dead.

The Irish professor was in the same team as Saray Khumalo, 47, who this week became the first black African woman to climb Everest and who is hoping to conquer the highest summits on each of the seven continents.