Who is Karl-Erivan Haub?
Haub, 58, is the chief of Germany's extensive Tengelmann retail group which includes the KiK low-cost clothing stores, OBI home improvement outlets, the Trei Real Estate group and part of the online fashion site Zalando. The group, which dates back to 1876, has 215,000 staff and revenues of some €30 billion, according to the company website.
What is his personal wealth?
His personal wealth is not known but the Haub family holds joint 265th place on Forbes magazine's global rich list and comes in 20th place in Germany. The family's wealth is listed at $6.4 billion.
How and when did Haub go missing?
Haub reportedly set off on Saturday morning for a solo ski tour from the Klein Matterhorn, above the popular alpine resort of Zermatt and, at 3,800 metres above sea level, the highest location in Europe reachable by cable car.
At a press conference on Wednesday, a spokesperson for police in the canton of Valais reported the businessman had last been seen at 9.10am on Saturday at the Klein Matterhorn cable car station.
A final video capture was taken of Haub at the cable car station but has not been released to the public because the family have yet to decide whether to consent to its publication, Valais cantonal police said on Thursday.
Why was Haub on the Klein Matterhorn?
According to Blick, Haub's family raised the alarm after the seasoned skier did not show up for an appointment at his hotel in Zermatt.
"We started the search on Sunday morning, after being informed that the skier had not returned," cantonal police spokesman Markus Rieder told news agency AFP.
What are his chances of survival?
Haub was described as an experienced mountaineer by his brother Christian in a letter to Tengelmann employees published by German business paper Handelsblatt.
"Despite the time that has passed since (his disappearance) we aren't giving up hope of finding him soon," Haub said in the letter.
But the last signal from Haub’s mobile phone was registered in the large Trockener Steg region at 8.33am on Saturday morning. “[He] could be almost anywhere,” said Anjan Truffer who heads up rescue services in Zermatt.
Axel Mann, a doctor with Zermatt rescue services said chances that Haub had survived were low given the possibility he had been injured and of hypothermia given the length of time he had been missing. But he stressed there was still a small chance and rescue efforts were ongoing.
Haub was reportedly wearing only light clothing and carrying a backpack.
Has family money played a role in the search?
Truffer said the family had thrown a lot of money at the search. “But that doesn’t make a difference to us, we are here to help. We carry out every search in the same way: as long as the security of the rescue workers is guaranteed, we keep searching,” he said.
What is the current state of the search?
The search for the 58-year-old magnate is concentrated in the Matterhorn, between the canton of Valais in Switzerland and Italy's Aosta Valley.
But despite clear skies over Zermatt on Thursday, rescue workers were unable to continue their search: strong winds meant helicopters were unable to bring teams to the search area, said Stéphane Vouardoux with Valais cantonal police.
On Wednesday rescuers battled driving snow and howling winds.
"The search resumed this morning [Wednesday], but because of bad weather, Air Zermatt helicopters have trouble flying over the area. There are also experienced rescuers who have used the lifts and are doing foot searches," said Zermatt cantonal police spokesman Rieder.
The search area covers thousands of hectares, while operations are coordinated with the Italian rescuers, he added.
Some sixty people and a number of dogs have been involved in the rescue to date, according to regional daily Le Nouvelliste.
Operations on the Italian side of have also been hampered after a wave of harsh weather hit the north of the country, said Delfino Viglione, an alpine rescuer for the Aosta Valley. This was lowering the chances of a rescue.
"The weather conditions, with gusts of wind and snow, are complicating the task for rescue workers, who are dealing with poor visibility," Viglione told AFP.
"The weather should improve at the end of the week, but it is clear that the more time passes, the worse our chances of finding him alive at such altitudes. The only hope is that he has found shelter."
Viglione said that rescuers were trying to track his mobile phone, "but it is likely that the battery has died since his disappearance".