The avalanches triggered by Saturday's earthquake in Nepal led to the worst disaster in the history of Mount Everest.
Eighteen people have been confirmed dead so far and rescue teams are racing to get to those who survived before their supplies run out.
People involved spoke to the BBC about how they are co-ordinating the rescue operation.
Who was there at the time?
Altogether 42 teams were attempting to scale Mount Everest at this point early on in the climbing season, according to Nepal's tourism ministry.
That means hundreds of mountaineers, all of them starting and ending their ascent at Everest Base Camp.
About 210 of them were trapped at either Camp 1 at a height of 6,400m (21,000ft) or Camp 2 at 6,750m when the avalanches hit, tourism department Director General Tulsi Gautam told the BBC.
The avalanches swept away their climbing ropes and ladders leaving them unable to come back down the mountain.
It was not until Monday that helicopters were able to reach Camps 1 and 2 to evacuate some of those trapped.
But many remain stranded at the two higher camps, according to Himalayan Guides Nepal, a local company providing logistics services to foreign tour operators.
Separately, about 300 trekkers are said to be trapped in the Langtang region, north of Kathmandu bordering Tibet.
Tourism department Director General Tulsi Gautam said the trekkers "are safe there, albeit without enough food and it's a bit crowded".
Among those who didn't survive the avalanche are five local guides working for one New Zealand tour company, Adventure Consultants. Their names have not been released.
A documentary-maker from Santa Monica, Tom Taplin, and a Google engineer, Dan Fredinburg, were also among those killed. Mr Fredinburg died from a head injury after the avalanches, according to the mountaineering company Jagged Globe that took him to Base Camp.
How well equipped are they?
Sherpas, porters and yaks usually carry supplies to Base Camp for their teams and a rudimentary camp is set up there where climbers spend a week acclimatising to the altitude.
Reports say some teams' entire camps were swept away by the avalanches, while others still have some supplies.
Steve Moffat, operations manager at Adventure Consultants, said guides and sherpas have qualifications and the experience to deal with situations of this kind.
"[Our teams] don't have a lot of supplies because their camp at Base Camp was badly damaged, but they are being accommodated by other teams," said Mr Moffat.
"Teams that weren't affected at Base Camp - those that were not directly hit - they have cooking facilities, they have food and fuel."
He said the company had now managed to get the rest of their team, 37 people, down to Base Camp.
How are they being evacuated?
The tourism ministry says more than 200 mountaineers have been rescued so far from Base Camp and brought to villages at lower altitudes or to Kathmandu for medical treatment.
Those in a critical condition were taken to a clinic in the village of Pheriche.
Helicopters are the only vehicles able to reach the higher camps but the altitude causes problems, weather conditions have to be good and finding a spot to land is very difficult.
Other government and private rescue operations were continuing on Monday.
"We have mobilised four small helicopters to airlift sick or injured climbers near the Base Camp," Tulsi Gautam said.
Iswari Paudel, the managing director of Himalayan Guides Nepal, said they had also sent four helicopters on Monday to bring people in their teams down from Camp 1 to Base Camp.
Those in Camps 1 and 2 are in touch using satellite phone and are being briefed on the arrival of helicopters.
They are prioritising those who need immediate medical help. He says the others have food and supplies to survive another day or two.
"From Camp 2 we can only pick up one person at a time. The altitude makes it hard to pick up more than one person. From Camp 1 we can pick up two or three at a time."
Mr Paudel says his company is co-ordinating rescues despite their own office in Kathmandu being badly damaged.
"We are not able to open our office, the landlines don't work, there is no electricity or water," he said. "I'm charging my mobile phone in my car."
Jim Davidson, a climber from the US who was among those trapped at Camp 1, updated his Facebook page on Monday saying he had now been evacuated to Base Camp.
Some tour agencies say they will not move people from Base Camp to Kathmandu, until accommodation and onward travel is sorted out.
Many buildings have collapsed in the capital and it continues to experience aftershocks. The airport has also suffered damage.
- First successful ascent was by New Zealand mountaineer Sir Edmund Hillary and Sherpa Tenzing Norgay on 29 May 1953
- More than 4,000 people have scaled the summit since then
- Hundreds of people attempt to climb Everest every year - 658 people made the summit in 2013
- More than 200 people have died trying to climb Everest