Rescuers have called off the search for three sherpa guides who remain missing after the deadliest ever accident on Nepal’s Mount Everest killed at least 13 of their colleagues.

Friday’s avalanche occurred as the group went up the world’s highest mountain with equipment and supplies to be used by foreign climbers in their efforts to reach the summit.

Sherpas are an ethnic group in Nepal and have helped foreigners climb the country’s towering peaks since before Sherpa Tenzing Norgay and New Zealander Sir Edmund Hilary became the first to reach the top in 1953.