A recent spike in deaths atop the tallest mountain in the world doesn't solely have to do with recent overcrowding but includes a myriad of other factors, a top official in Nepal said Sunday.

About half a dozen climbers died this past week, most while descending from the summit of Mount Everest during only a few windows of good weather each May.

Most are believed to have suffered from altitude sickness, which is caused by low amounts of oxygen at high elevation and can cause headaches, vomiting, shortness of breath and mental confusion.

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A recent photo showed a line of climbers attempting to stand at the summit in the area 26,200 feet above sea level called "the Death Zone." Nepal's tourism ministry has issued a record number of permits to 381 climbers this season, one reason that tour organizers have highlighted the overcrowding on the mountain.

Gyanendra Shrestha, a liaison officer at the Everest base camp, told The Himalayan Times that climbers who reached above Camp IV complained of waiting for more than two hours on May 22 in bottleneck lines on their way to the summit.

“Everyone seems in a hurry to reach the summit point when the weather is clear," he told the newspaper.

The head of Nepal's tourist department, Dandu Raj Ghimire, told the BBC on Sunday that while the number of climbers on the routes has been "higher than expected," there are other factors at play. He did not specify what those were.

"Mountaineering in the Himalayas is in itself an adventurous, complex and sensitive issue requiring full awareness, yet tragic accidents are unavoidable," he said.

Ghimire also put the current death toll at 8, even though 10 people have been reported dead or missing in the past week.

One of the dead included British climber Robin Haynes Fisher, who warned of long lines at the summit just hours before his death.

In an Instagram post, Fisher conveyed his fears about the overcrowding and waits in the "Death Zone' and that he previously changed his plans to avoid the crowds.

"With a single route to the summit delays caused by overcrowding could prove fatal so I am hopeful my decision to go for the 25th will mean fewer people," he wrote. "Unless of course everyone else plays the same waiting game."

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The 44-year-old climber died on Saturday minutes after reaching the summit, according to the BBC.

An American climber is also among the recent deaths atop Everest. Don Cash, 55, became ill at the summit and was treated there by his two Sherpa guides, Pasang Tenje Sherpa, head of Pioneer Adventure, which provided the guides, said Friday.

"When he was on the top he just fell. The two Sherpas who were with him gave CPR and massages," he told the Associated Press. "After that he woke up, then near Hillary Step he fell down again in the same manner, which means he got high altitude sickness."

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The Press Trust of India news agency reported Friday that two more Indian climbers died on Mount Everest together with an Austrian while descending from the summit this week.

Also, the U.K.-based climbing company 360 Expeditions said that an Irish climber died Friday while attempting to climb Everest.

Fox News' Ryan Gaydos, David Aaro, Nicole Darrah and The Associated Press contributed to this report.