May 1 (UPI) — Authorities said six people have died from a snowstorm that stranded a group of Alpine hikers in the Alps of southwestern Switzerland.

Valais Police said 14 became trapped in the area of ​Pigne d’Arolla on Sunday, following a sudden snowstorm and high winds.

Officials said an Italian national was killed in a fall, and four others died later at the hospital. A 52-year-old Bulgarian citizen was confirmed dead Tuesday.

Three others are in critical condition, officials said. Three French citizens, a German and an Italian had hypothermia.

Swiss police said relief resources were “immediately engaged​” to help the hikers.

Seven helicopters from Air-Glaciers, Air-Zermatt and REGA, with several doctors and lifeguards, were dispatched to help the stranded group.

The Swiss Public Ministry will investigate the incident.