An avalanche on Mount Everest has killed at least 12 Nepalese guides early Friday morning. It is the single deadliest accident at the world’s tallest summit.

The accident occurred around 6:30 a.m. as the Sherpa guides tried to fix ropes along a climbing route near Camp 2, Nepal Tourism Ministry official Krishna Lamsal told The Associated Press. Suddenly, an avalanche hit near Camp 2.

During the search for any survivors, 12 bodies were found and thee guides who were critically injured. According to the Himalayan Times, eight in total have been rescued alive and five remain missing.

There are hundreds of climbers and guides in the area now, as they prepare for the best time of year to reach the summit. Weather conditions are at their best in early May and the guides were further up the mountain to prepare for the international climbers who hope to scale the mountain. Over 4,000 people have reached the top since it was first done in 1953. The peak is at 29,028 feet.

According to CNN, this was the deadliest accident at the mountain. Previously, the deadliest accident was in May 1996, when eight people went missing during a storm.