KATHMANDU, Nepal - According to sources, Luis Stitzinger, the expedition leader of the German operator Amical Alpin, has remained out of contact from around 8,500m after scaling the world's third-highest peak without using supplemental oxygen on May 25.

According to Thaneswar Guragai, General Manager of Seven Summit Treks, a search mission has already been launched to find the missing alpinist. Luis was last seen descending at approximately 8,500 meters.

On May 25, Luis stood atop the mountain with Adrian Laza, Vadim Pirmin Druelle, Vibeke Andrea Sefland, He Jing, Waldemar Kowalewski, Flower Waganku Wayta, Pemba Sherpa, Nuri Sherpa, Chhepal Sherpa, Chhiring Bhote, and Ang Tenji Sherpa.

Luis, an officially certified mountain and ski guide, was born in Fssem in 1968 and had been exploring the mountains since he was a child. He has been one of Germany's most active mountaineers for many years. He has climbed many mountains without using bottled oxygen.