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The Lead Masks Case was the name given to the events which led to the death of two Brazilian electronic technicians: Manoel Pereira da Cruz and Miguel José Viana. Their bodies were discovered on August 20, 1966.

The bodies were next to each other, slightly covered by grass. They were wearing suits, and impermeable coats. There was no sign of violence to the bodies or to the surrounding area. Next to the bodies, the police found an empty bottle of water and a packet containing two towels. What really caught people’s attention were the lead masks worn by the men. They were masks typically used for protection from radiation, and it is these masks that have given the case its name. To make things more complicated, the policemen found a small notebook with signs and numbers, and also a letter in which was written: “16:30 estar no local determinado. 18:30 ingerir cápsulas, após efeito proteger metais aguardar sinal máscara” (16:30 be at the agreed place. 18:30 swallow capsules, after effect protect metals wait for the mask sign).

Gracinda Barbosa Cortino de Souza and her children, who live next to the hill where the men died, claimed that they had seen a UFO flying over the spot at the exact moment the detectives believed the two men must have died.[