Makalu, Nepal - A US climber attempting to scale the world's fifth-highest mountain, Makalu, his expedition organizer said Monday, marking the second death of this climbing season.

Alexander Pancoe died at Camp 2 of the 27,838-foot Makalu on Sunday evening.

"He had descended after an acclimatization rotation to Camp Three, and was not feeling well," Iswari Paudel of Himalayan Guides Nepal, told AFP.

Paudel said that attempts were being made to bring the 39-year-old's body down.

An accomplished climber, Pancoe had survived a brain tumor when he was younger.

He had completed the Explorer's Grand Slam, a challenge that involves climbing the highest peak on each of the seven continents and then skiing to both the North and South Pole.

Pancoe was recently fighting chronic myeloid leukemia and was attempting to climb Makalu to raise funds for the pediatric blood cancer program of the Lurie Children's Hospital, based in Chicago.

"It's going to be a huge challenge for me – climbing at altitude is plenty hard without a chronic ailment – but I look forward to rising to the challenge," he said on his website Peaks of Mind.

An Austrian climber died while descending Nepal's Ama Dablam after a successful summit last month, the first death of the summit season.

Nepal is home to eight of the world's 10 highest peaks, including Mount Everest, and welcomes hundreds of climbers every year during the spring and autumn climbing seasons.

It has already issued nearly 500 permits for its mountains this season, including 214 for Everest.