(CBS News) KATMANDU, Nepal -- An avalanche swept Mount Everest's slopes on Friday along a popular route used to climb the world's highest peak, killing at least 12 Nepalese guides and leaving three missing in the worst disaster to hit climbers on the mountain, officials said.
The Sherpa guides had gone early in the morning to fix ropes for other climbers when the avalanche hit them just below Camp 2 at about 6:30 a.m., Nepal Tourism Ministry official Krishna Lamsal said from the base camp where he was monitoring rescue efforts.
Rescue workers pulled out 12 bodies from under mounds of snow and ice and were searching for the three missing guides, Lamsal said.
Two Sherpas who were injured were taken by helicopter to hospitals in Nepal's capital, Katmandu.
The Reuters news agency says three guides were injured and up to five people were missing.
Hundreds of climbers, their guides and support crews have gathered at the base camp to prepare for attempts to scale the 29,035-foot mountain early next month when weather conditions become favorable. They have been setting up camps at higher altitudes and guides have been fixing routes and ropes on the slopes above.
As soon as the avalanche hit, rescuers and fellow climbers rushed to help.
Ang Tshering, of the Nepal Mountaineering Association, said the area where the avalanche hit is nicknamed the "popcorn field" and is just below Camp 2, at 21,000 feet.
Earlier this year, Nepal announced several steps to better manage the heavy flow of climbers and speed up rescue operations. The steps included the dispatch of officials and security personnel to the base camp at 17,380 feet, where they will 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 Edmund Hillary and Sherpa Tenzing Norgay. Hundreds have died attempting to reach the peak.
The worst recorded disaster on Everest had been on May 11, 1996, when eight climbers were killed in one day because of a snow storm near the summit. Six Nepalese guides were killed in an avalanche in 1970.
Everest sits on the border between Nepal and the Chinese region of Tibet, and can be climbed from both sides, Reuters points out.
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