Children aged between 11 and 14 are reportedly fainting and having strong muscular convulsions.
Shocking video footage shows pupils who are barely conscious, repeatedly screaming, and who appear to be delirious.
Doctor Antony Choy told national channel Panamericana TV: “We don’t understand how this has kept on going on.
"We know it started on 29th April and now it is still happening. Now there are almost 80 pupils [still affected].”
Elsa de Pizango, a concerned mother whose daughter has experienced some of the symptoms, said: “She fainted in school. They didn’t say anything at the hospital. She just fainted. She keeps on spitting froth from her mouth.”
A pupil, not named in local media, described their experience: “It’s disturbing for me to think about it. It’s as if someone kept on chasing me from behind. It was a tall man all dressed in black and with a big beard and it felt like he was trying to strangle me.
"My friends say I was screaming desperately, but I don’t remember much.”
Another schoolgirl said she had trouble breathing and was desperately holding her neck as if someone was strangling her. According to her friends, she kept screaming: “Take it out.”
Another anonymous girl, aged 13, told local media: “Several children from different classrooms fainted at the same time. I got nauseous and started vomiting. I heard voices. A man in black chased me and wanted to touch me.”