The climbers who each year attempt to follow in Tenzing Norgay and Edmund Hillary's footsteps to the summit of Mount Everest are threatening to bring environmental disaster to the roof of the world - by their toilet habits.
The head of Nepal's mountaineering association, Ang Tshering, has warned that human waste left when climbers use holes in the snow as toilets is contaminating the world's highest peak.
About 700 climbers spend almost two months every year on Everest's slopes when conditions allow climbers to reach the peak - from this week until May - and are leaving large amounts of faeces and urine buried in the snow.
Tshering said Nepal's Government needs to get the climbers to dispose of waste properly, so the mountain remains pristine.
Climbers have returned to Everest base camps for the first time since last year's expeditions were cancelled after an avalanche killed 16 local guides.