Helicopters airlifted the group to safety after they were spotted early on Sunday at a base camp near India's second highest mountain, the 7,826-metre (25,643-foot) Nanda Devi.
The video clip of four Britons, two Americans, an Australian and their Indian guide roped together in bright sunshine as they take nervous, synchronised steps along a narrow ridge towards a snow-capped peak.
"Some bodies were visible during the helicopter recce. They were on the same route as the climbers had taken," the source said, requesting anonymity.
A man who became wedged between rocks while collecting bat droppings in the Cambodian jungle has been rescued after almost four days.
Dozens of mountaineers have been competing over the past few weeks to summit the world's second highest mountain, the last peak above 8,000 metres to be topped in wintertime.
Goldfarb pushed on alone when his teammate failed to persuade him to give up during an acclimatising mission, ahead of a bid to scale the nearby 8,051-metre (26,414-feet) Broad Peak in the Karakoram range on the Chinese border.
The announcement brings closure to a dramatic tragedy on one of the most dangerous mountains to climb in the world. K2 had never been scaled in winter until only last month, when a Nepalese team reached the peak. Sadpara's son, Sajid told reporters that he was grateful authorities had done their best to try to find the group.
Their ascent in mid-January of the world's second-highest mountain — the notoriously challenging K2 mountain of Pakistan — shone a much-deserved spotlight on their own climbing prowess.
“It’s already been more than 30 hours, we have received no news of John Snorri, Ali Sadpara, and Juan Pablo Mohr, since none of the GPS trackers seem to be working,” Chhang Dawa Sherpa, their expedition manager, said in a statement. An army helicopter has conducted a search flight for the missing climbers, Sherpa said.