Four people died climbing Mount Everest in four separate incidents over the weekend. An American doctor from Alabama was one of the victims.

There are growing concerns the world's tallest mountain is overcrowded, making the climb even more dangerous.

It's a record year on Mount Everest. Nepalese authorities have issued more than 370 climbing permits to foreigners, the most since they started regulating the climb in 1953.

A February 2016 file photo of trekkers passing through a glacier at the Mount Everest base camp in Nepal. Tashi Sherpa/AP

At least 150 people are trying to summit the mountain Monday and Tuesday.

After an avalanche in 2014, followed by an earthquake in 2015, Everest climbing returned to some sense of normalcy last year. But this new normal can be chaotic, Jeff Glor reports, with more guides competing for business and more aspiring climbers willing to hire them.

Roland Yearwood. Facebook

One of them was 50-year-old Roland Yearwood, a primary care doctor from Georgiana, Alabama. He reportedly survived a 2015 avalanche on Everest that killed 18 people, only to die attempting a climb Sunday morning. He was less than 2,000 feet from the summit, in an area known as Everest's "death zone."

"This is an area where the oxygen content drops to less than 35 percent," said climber Jon Kedrowski, a doctor who summited Everest in 2012. "Because of the lack of oxygen, the body starts to literally consume itself, and when that happens, the body will shut down."

Kedrowski says the large number of climbers causes traffic jams near the top, where dozens of mountaineers often stack up single-file waiting to reach the peak.

"People can be up there standing in line for three hours, then they run out of oxygen, and then the weather moves in," he said. "So you have all these factors that sort of compound into tragedy."

Climbers Adrian Ballinger and Cory Richards are documenting their push to Everest's summit on social media and the website everestnofilter.com. Earlier this month they described how they coped with a death on the mountain.

"It's a reminder to really make sure that it's still worth it," Richards said, "that our values are in the right place, that we're doing this for the right reasons, and we're willing to accept that risk."

Ballinger and Richards are still hoping to summit early next week, despite the latest tragic news.

The three other climbers who died this weekend were from Australia, Slovakia and India.

Six climbers have perished on Everest so far this year.