KATHMANDU, Nepal — Three climbers — one from Alabama, one from Slovakia and the third an Australian — died Sunday on Mount Everest, the world’s highest peak, and an Indian man disappeared while descending, officials and expedition leaders said.

Dinesh Bhattarai, the director general of Nepal’s Department of Tourism, said the American climber, Dr. Roland Yearwood, 50, a physician, died near the summit of the mountain, at 8,400 meters, or 27,600 feet. The cause of his death was not immediately known.

Another official with the department, Gyanendra Shrestha, said later Sunday that a man from Slovakia, Vladimir Strba, part of a separate expedition, also died. Mr. Strba, 48, died at a camp at an elevation of about 8,000 meters, Mr. Shrestha said.

The Australian man was identified as Francesco Marchetti, 54, by the Adventure Thamserku Treks and Expeditions company. He developed altitude sickness around 8,600 meters and was trying to descend the mountain when he died, said Dawa Geljen Sherpa, the company’s managing director.