KATMANDU, Nepal â€"  A German doctor has died while descending from the Everest summit, and a Nepalese official says four other climbers may be missing on the world's highest mountain.

Ang Tshering of the Asian Trekking in Katmandu said 61-year-old Eberhard Schaaf died Saturday. Doctors believe he had high altitude cerebral edema.

Kamal Shrestha of Nepal's Mountaineering Department said a Nepal-born Canadian national identified as Shriya Shah is also missing on the mountain.

Shrestha said he has heard of a Korean, a Chinese and a Nepali Sherpa guide missing on their way back but did not have any more details.

May is the busiest month for climbing attempts on the 29,035-foot summit.