An avalanche on Mount Everest killed 12 Sherpa guides and injured six others on Friday, which is now being dubbed the deadliest day on the mountain. Four others are reportedly still missing.

12 Die In Mount Everest Avalanche

Fifty individuals, mostly Nepali Sherpas readying the route up Everest for the busiest climbing season of the year, were in the path of the avalanche when it occurred at an altitude of 20,000 feet, according to Nepal Tourism Ministry’s Tilak Ram Pandey, reported CNN. The avalanche occurred right near the Khumba Ice Fall base camp.

All 12 of the deceased were Sherpa guides. All of the climbers, who were on the mountain to grow accustomed to the climate and altitude, have been accounted for, while rescuers continue to search the area for the four missing.

Climbers generally attempt to take the mountain between May 15 and May 30, as that’s believed to be the safest time for the hike. For the spring season, 334 individuals are scheduled to try to make their way to the top. They’re to be aided by roughly 400 local Sherpas.

Prior to Friday, the deadliest day on Everest was in May 1996, when a huge storm hit the mountain, leaving eight climbers dead. The tragic event was immortalized in Jon Krakauer’s Into Thin Air.

– Chelsea Regan