An avalanche swept down a slope of Mount Everest on Friday along a route used to ascend the world's highest peak, killing at least 13 people in the mountain's deadliest disaster.
NBC News confirmed that all of the dead were Sherpa guides.
The guides had gone early in the morning to fix the ropes for hundreds of climbers when the avalanche hit them just below Camp 2 around 6:30 a.m. local time, Nepal Tourism Ministry official Krishna Lamsal told The Associated Press.
Tilak Ram Pandey, an official at the ministry's mountaineering department, later told Reuters that some other people were thought to be missing.
Hundreds of climbers, their guides and support guides had gathered at the base camp, gearing up for their final attempt to scale the 29,035-foot peak early next month when weather conditions get favorable. They have been setting up their camps at higher altitudes and guides fixing routes and ropes on the slopes ahead of the final ascend to the summit in May.
As soon as the avalanche hit, rescuers and fellow climbers rushed to help. A helicopter was also sent.
Ang Tshering of the Nepal Mountaineering Association said that the area where the avalanche occurred is nicknamed the "popcorn field," which is just below Camp 2 at 21,000 feet.
Nepal had earlier announced several steps this year to better manage the flow of climbers, minimize congestion and speed up rescue operations. The preparations included the dispatch of officials and security personnel to the base camp located at 17,380 feet, where they would stay throughout the spring climbing season that ends in May.
More than 4,000 climbers have scaled the summit since 1953, when it was first conquered by New Zealander Sir Edmund Hillary and Sherpa Tenzing Norgay. Nearly 250 others have died on the mountain.
The worst recorded disaster on Everest was on May 11, 1996, when eight climbers were killed in one day because of a storm near the summit. Six Nepalese guides were killed in an avalanche in 1970.
— Sarah Burke of NBC News, Reuters and The Associated Press contributed to this report.