I don't think anyone has direct evidence for arsenic. It is just one possible physical explanation for the reported illness. Andean waters are often high in arsenic because of leaching of hydrothermal deposits. But it is a hypothesis only. I suspect that the most likely cause of illness is the shock of having something like this come down in your back yard.

There is no evidence that this is a satellite reentry. No fragments of machined alloys mentioned. There are reports of chrondritic material and metallic iron. All evidence for a meteorite.

Jon