Mountain guide Olivier Sourzac, 47, and his client Charlotte Demetz, 44, successfully climbed the classic north face route of The Shroud, and made the summit, before being caught in a terrible storm. The pair, who are believed to be well equipped, are reportedly stuck on the Roches Whymper on the south side of the mountain due to the freezing wind and heavy snow, and have been out of telephone contact for some days now.

Today, their fifth at an altitude of around 4000m, has seen another thwarted attempt at a helicopter rescue. Deep, fresh snow and poor visibility has meant that rescue teams both on foot, and in the air, have been unable to reach the climbers over the past few days.

Sourzac's brother, also a mountain guide, has himself tried to reach the climbers on foot from the nearby mountain refuge of the Boccalatte hut, but to no avail.

Chamonix based mountain photographer Jon Griffith, who climbed The Shroud himself just two weeks ago on a photo-shoot, commented on the situation:

"It's incredibly hard to comment on anything like this. However it is one of those occasions where everyone on both sides of the Mont Blanc massif have been thinking about them both day and night. The rescue services as well as friends and family of both climbers have gone above and beyond over the last 4 days to try and make contact and get them off the mountain.

It's hard to understand what they must be going through but the south side of the Jorasses during the Foehn must be a terrifying place to be - a combination of howling winds, freezing temps, and heavy snowfall. The descent even in normal conditions is incredibly involved. I can barely imagine how both heart wrenching and infuriating it must be for his brother to be stuck 1000m below him at the Boccalate hut unable to make any further progress up the mountain due to the deep snow and avalanche risk. Tomorrow looks to be a better day, fingers crossed for all."

The Roches Whymper, where the climbers are reported to be stuck, is on the descent on the south side of the mountain.

Jon explained the lay-out:

"You've got the Walker Spur on the far left, then the Whymper Spur on the right of it. The Roches Whymper comes down the south side of the Wymper summit. It's a low-angled spur of rock. It is generally slower than walking off the normal route, but a better choice in poor visibility as you can navigate by following the rock spur down."

• Italian local climber and UKC regular Luca Signorelli has been reporting updates on the situation in the UKC Forums.

There is a local news report (in French) on the climbers here: ledauphine.com