Helicopters flew over an area near Switzerland’s Matterhorn mountain on Monday in hopes of finding a missing skier after five other members of the group were found dead after freezing to death in “catastrophic” conditions, Reuters reported.

The skiers, five members of one family from the canton of Valais, went missing on the Zermatt-Arolla ski run on Saturday.

Authorities did not give a cause of death for the five found Sunday night, but described “catastrophic” conditions with snowstorms, high winds and extreme temperatures.

“Our priority is to find the sixth person,” the head of the cantonal police, Christian Varone, told reporters.

“As long as there is hope, we will do everything we can, but we have to be realistic about the conditions that this person has been through in the last 48 hours.”

Mountain guide Anjan Truffer told Swiss broadcaster SRF that two bodies had to be pulled out from under the snow.

“The end result was obvious, people froze to death. They got caught in a storm, probably lost their bearings and didn’t know what to do.”

According to him, the rescuers advised them to dig a snow shelter after one of them raised the alarm.

“They tried, but unfortunately they were very ill-equipped and with those hard snow shovels they couldn’t do much.”

The incident is one of the worst in the Swiss Alps in recent years.

Eleven helicopters took part in the search and rescue operation over the weekend, along with a team of five who set off from Zermatt on foot to reach the area near the Matterhorn, which straddles the border between Switzerland and Italy.