Another three guides remain missing and searchers are working quickly to find them in case weather conditions deteriorate, said Maddhu Sunan Burlakoti, head of the Nepalese government's mountaineering department.
But the painstaking effort involves testing the strength of newly fallen snow and using extra ropes, clamps and aluminium ladders to navigate the treacherous Khumbu icefall, a maze of immense ice chunks and crevasses.
The avalanche slammed into the guides at about 6.30am local time yesterday near the "popcorn field", a section of the Khumbu known for its bulging chunks of ice.
The group of about 25 Sherpa guides were among the first people making their way up the mountain this climbing season. They were hauling gear to the higher camps that their foreign clients would use in attempting to reach the summit next month.
One of the survivors told his relatives that the path had been unstable just before the snow slide hit at an elevation near 19,000ft. The area is considered particularly dangerous due to its steep slope and deep crevasses that cut through the snow and ice covering the pass year round.
As soon as the avalanche occurred, rescuers, guides and climbers rushed to help, and all other climbing was suspended.
Seven of the 12 bodies pulled out and brought down yesterday were handed over to their families in the Everest region, while the other five were taken to Katmandu, Nepal's capital.
Four survivors were conscious and being treated in the intensive care units of several Katmandu hospitals for broken ribs, fractured limbs, punctured lungs and skin abrasions, according to Dr CR Pandey from Grande Hospital. Others were treated for less serious injuries at the Everest base camp.
Hundreds of climbers, guides and support crews had been at Everest's base camp preparing to climb the 29,035ft peak when weather conditions are most favourable next month. As with each year, the Sherpa guides from each of the expedition teams had been working together to prepare the path by carving routes through the ice, fixing ropes on the slopes and setting up camps at higher altitudes.
One of the injured guides, Dawa Tashi, said the Sherpas were delayed on their way up the slope because the path was unsteady. With little warning, a wall of snow crashed down on the group and buried many of them, according to Tashi's sister-in-law Dawa Yanju. Doctors said Tashi, who was partially buried in the avalanche, suffered several broken ribs.
The Sherpa people are one of the main ethnic groups in Nepal's alpine region, and many make their living as climbing guides on Everest and other Himalayan peaks.
The worst recorded disaster on Everest had been a fierce blizzard on May 11, 1996, that caused the deaths of eight climbers, including famed mountaineer Rob Hall, and was later memorialised in the book Into Thin Air by Jon Krakauer.
Six Nepalese guides were killed in an avalanche in 1970.
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 17,380ft, where they will stay throughout the spring climbing season, which ends in May.