According to this source
(in Portuguese), they were tested some time after, the bodies
were exhumed and tested again, and this time they tested for radiation, but nothing was found.
(also in Portuguese) has some photos, and it has more detailed information, that I
The bodies were found on a "bed" made with palm-tree leaves.
The autopsy did not show any signs of violence, poisoning, organic failure or radiation contamination.
The note was written by Miguel José Viana.
The masks were made on their shop, the rest of the lead sheet was found there.
They were seen arriving near the Morro do Vintém (a "morro" is somewhat like a hill) on a jeep with two other men, that were not identified.
The bodies were first found on the 18, and a policeman was warned by the boy who found them, some people suspect that this policeman was the one who
took the money they had (around 1000 dollars).
A friend of both was interrogated but he was not arrested, he had introduced both to some strange experiments to try to communicate with spirits, and
the three were responsible for a large explosion on a beach.
A priest and parapsychology professor said that they could have been making an experiment to see to the "other world", some people apparently say
that there is a very strong light for which protection is needed, and that people who make that experiment take some kind of drug before.
Apparently, four years before, a television technician died in the same place in similar circumstances; no signs of violence, no other objects and a
lead mask. He was trying to catch a "television signal" without any electronics and he died after taking a round pill.
The second batch of exams was made one year latter.
In 1980, Jacques Vallée went to that place to study the case, and the area was clean of vegetation and the bodies were like imprinted on the ground,
the ground looking like it had been burned.