Updated

Two experienced climbers have fallen to their deaths on Alaska's Mount McKinley.

National Park Service rangers recovered the bodies of 39-year-old John Mislow of Newton, Mass., and 36-year-old Andrew Swanson of Minneapolis.

The climbers, both doctors, were roped together when they fell Thursday afternoon along Messner Couloir, a steep, hourglass-shaped snow gully on the 20,320-foot mountain, North America's tallest peak. The climbing partners began an ascent of the mountain's West Rib route on May 30.

Park Service spokeswoman Maureen McLaughlin said many factors about the fall remain unknown, including its starting point and whether the climbers were descending or still ascending the mountain, which is in Denali National Park and Preserve. Climbers are not required to disclose their descent route, although some do anyway. Mislow and Swanson did not.

Rangers hope to learn more after viewing photographs in cameras belonging to the climbers, as well as from interviews with other climbers.

McLaughlin said the men fell at least 2,000 feet to Messner Couloir's base at 14,500 feet. Other climbers saw at least part of the fall, she said.

Rangers at the 14,200-foot camp were notified by radio within minutes of the accident. Three skiers in the vicinity were first to reach the climbers.

The deaths were confirmed by rangers, including medics, who were following close behind. The bodies were recovered by helicopter Thursday evening.

Rangers say Mislow and Swanson were seasoned mountaineers. In 2000, the two received the Denali Pro Award in recognition of setting the highest standards of mountaineering for safety, self-sufficiency and assistance to fellow climbers.

The two helped several teams in distress that year and assisted with visitor protection projects, McLaughlin said.

Swanson, who was single, was an orthopedic surgeon and practiced alongside his father, Gene, and older brother, Kyle, at the Orthopaedic and Fracture Clinic in Mankato, Minn., where he grew up. Each day, he commuted 60 miles from Minneapolis to the northeast, staying with his parents if he was on call, said his mother, Eydie Swanson. Kyle Swanson headed to Alaska on Friday to bring home his brother, she told The Associated Press in a phone interview.

While on Mount McKinley, Andrew Swanson called his parents every two days from his satellite phone. They last heard from him Tuesday, when he said the plan was to summit on Wednesday. If they couldn't summit on Wednesday, the two planned to turn around and head down.

Another call announcing the summit was expected but never came, Eydie Swanson said. That made her uneasy, but she reasoned the satellite phone had given out.

Eydie Swanson's voice broke as she talked about her son. She said he was a pilot and was passionate about climbing and bicycling. Most of all, she said, he loved donating his time twice a year in Africa as part of a mission working with children with severe spine deformities.

"He had the most wonderful face in the world," Eydie Swanson said. "He was so handsome, so kind, so irresistible. If you knew him, you loved him."

Mislow, a neurosurgeon, was married with children, McLaughlin said. He was a resident in the neurosurgery department at Brigham and Women's Hospital in Boston.

Mislow's family was requesting privacy for the time being, according to department chairman Arthur L. Day, who called Mislow a brilliant surgeon and researcher.

He was tirelessly dedicated to excellence, and always exhibited and demanded the best of himself and others in personal ethics and performance," Day said in a prepared statement. "His death is devastating to us all; the world has lost a great light, and his presence will be sorely missed."

Mislow and Swanson's deaths bring to four the number of fatalities at McKinley this climbing season, which runs through early July. There were four deaths in the entire season last year. The most deadly season was in 1992, a bad storm year, when 11 people died on the mountain, McLaughlin said. Many years there are no fatalities. Altogether, 106 people have died on McKinley since 1932, when the first two deaths occurred, according to Park Service statistics.

In early May, 61-year-old climber William Hearn of Fairport, N.Y., collapsed after this team reached 13,500 feet and was pronounced dead soon after. On May 19, 41-year-old Gerald Myers, a chiropractor from Centennial, Colo., vanished after he left his climbing partners at 14,200 feet to make a solo summit attempt. His body has not been found, but McLaughlin said he is presumed dead. Searchers looking for him located the bodies of two Japanese climbers who went missing last year.