A 15-year-old US citizen is among the dead in the Easter weekend avalanche in Switzerland’s Zermatt municipality, police reported on Tuesday. The dead include a man and a woman, whose bodies have been recovered, but who have not as yet been identified. A fourth skier caught up in Monday’s avalanche, a 20-year-old Swiss national, was flown to hospital with serious injuries. The search for other possible victims was called off on Monday evening, a few hours after the avalanche came down on an off-piste area of the Riffelberg, which lies below the Matterhorn. Avalanche warnings had been issued. S…