May 26 (UPI) — Five skiers were found dead on a Swiss mountain near Zermatt over the weekend, authorities said.

According to a statement Sunday from southern Switzerland’s Valais cantonal police, the five bodies were discovered Saturday on the Adler Glacier by emergency responders aboard an Air Zermatt helicopter conducting an aerial survey near the mountain resort of Zermatt.

The authorities launched the search after being alerted by two mountaineers to skis abandoned at an altitude of about 13,125 feet on Rimpfischhorn mountain.

Police said the two ski mountaineers on Rimpfischhorn noticed the abandoned skis at the base of the summit at about 4:30 p.m. local time on Saturday.

Air Zermatt added in a separate statement that it was four pairs of skis that the mountaineers had first seen as they ascended the mountain. On their way back down, the mountaineers again noticed the skis, which had remained untouched.

Three bodies were discovered during the aerial search in what Air Zermatt called an avalanche cone on the mountain. Two more bodies were found about 650 feet higher up on the mountain in a small snow patch, the emergency air transport company said.

The fifth pair of skis was also found in the area, it added.

Identification of the bodies is underway, police said. The local prosecutor’s office has launched an investigation to determine the cause of the deaths.