Police in Switzerland’s Valais canton on Sunday were searching for six people who went missing during a ski tour that departed from the Alpine town of Zermatt.

The police in Valais did not immediately respond to a Reuters request for comment.

The skiers, five of them members of the same family, went missing around Tete Blanche mountain on Saturday on the Zermatt-Arolla path, near the Matterhorn mountain that straddles the border between Switzerland and Italy, police had said earlier.

A storm raging in the south of the Alps and the risk of avalanches prevented helicopters and rescuers from approaching the area, police said.

The skiers were between the ages of 21 and 58, according to police. Five belonged to one family from the Valais canton, while a sixth person is from the canton of Fribourg.

Zermatt is a popular mountain resort renowned for skiing and attracts tourists from around the world.