Hope of finding the noted partnership of Argentinian Mariano Galvan, and the Spanish-Basque Alberto Zerain, who were attempting an alpine-style ascent of Nanga Parbat's Mazeno Ridge, has now faded after an aerial search on the morning of the 1st July.
In recent years the two climbers have formed a strong partnership at high altitude.
Zerain (55) had climbed 10 of the 8,000m peaks, all without supplementary oxygen (including Everest), while Galvan (37) who had established speed records on Aconcagua and soloed its south face, had climbed seven, again including Everest and all without oxygen.
With Txingu Arrieta, Zerain attempted the Mazeno Ridge in 2011 via a previously unclimbed start, but was defeated by bad weather.
The following year the much sought-after and much tried line was finally completed by Sandy Allan and Rick Allen.
In May this year Zerain reached the summit of Annapurna, while Galvan was already well acclimatized, so the two wasted no time before starting on the route.
They arrived at the standard base camp (ca 4,200m) on the Diamir side of the mountain on the 15th June, and over the next couple of days ferried loads to the base of the ridge at around 4,500m.
They left base camp on the 18th to begin the climb, with a forecast that suggested at least one day of bad weather would probably interrupt progress in a couple of days time.
When Allan and Allen made their historic ascent in 2012, they took 18 days to climb the ridge and descend the Kinshofer Route to Diamir base camp.
The undertaking is so long that there is almost zero chance of completing it in a stable period, so Galvan and Zerain knew they would have to sit out periods of bad weather while on route.
They made good progress on the 19th ascending more than 1,000m, reaching the ridge and camping for the night at ca 5,600m.
However, it then started to snow. According to Zerain, who was able to communicate with friends at home, warm temperatures meant that the snow was wet, and their wait was proving quite uncomfortable.
The forecast proved to be wrong, and the two were stuck in the tent until the 23rd, when they appear to have moved up to around 6,000m. Zerain reported he and Galvan were in great shape and were happy with their progress so far, though they now hoped to complete the ridge quickly before the weather broke again.
On the 24th the tracker that Zerain was carrying showed the pair moving for around six hours to an altitude of 6,270m. Yet about an hour later the tracker's position was 180m distant from this point and almost the same number of metres lower, at 6,112m.
For the next 15 hours the tracker sent a good signal from exactly the same location until it shut down. The tracker also had the facility for sending an emergency distress signal, but this was not activated.
Rescue helicopters in Pakistan are supplied by the military and one was able to fly from Skardu on the 28th, collecting a Romanian climber at Nanga Parbat base camp, and scouring the ridge for three hours. However, there was much cloud cover on the mountain and it was impossible to see the ridge at the point where the tracker had last emitted signal.
Bad weather then prevented further flights until the morning of the 1st July, when a helicopter was able to make two outings along the ridge in good visibility, reaching an altitude of 7,400m. Unfortunately, it was clearly seen that the location of the tracker was in an area of avalanche debris, the trigger point further up slope towards the crest of the ridge.
An official statement after the flight said that, sadly, this situation "leads us to rule out the possibility of survivors".