A 15-year-old American was among three people killed on Easter Monday in an avalanche near a Swiss ski resort, local authorities said Tuesday. The avalanche struck at about 2 p.m. Monday in an area outside the marked ski slopes at the Zermatt resort. Dozens of rescuers joined in a search for survivors, but the teenager and two others were already dead by the time they were found. “The deceased are a 15-year-old American as well as a man and a woman whose identification has not yet been completed,” police in Valais said in a statement. A 20-year-old Swiss man survived the avalanche but suffered serious injuries and was flown to a hospital, police said.