Kathmandu, Feb. 28 -- All three winter expeditions planned on Mt Everest have been called off due to threats of avalanches following the accumulation of fresh snow deposits on the world's highest peak.

Nepal's winter season officially ends on Saturday and along with it, the climbing permits issued for a winter expedition become invalid.

Expedition organisers said that the mountain received heavy snowfall for two consecutive days-starting February 25-amassing large snow deposits on the higher reaches of the mountain. These deposits risk causing avalanches when they are blown down to the lower reaches by high winds. The snow also obstructs the Khumbu Icefall, among the most treacherous sections on the Everest route, causing difficulties i...