I am aware, that this is a well-known thing, but still it is interesting and there might be some correlations to the Pass incident.
This event happened in August 1951 in the small French town Pont-Saint-Esprit, when mass psychotic chaos along with various physical symptoms (starting with nausea, stomach cramps, vomiting and diarrhea, then worsen) struck nearly 250 people, resulting in about 50 of them interned in mental asylums and 5 deaths. The reason for that event vary from food poisoning (ergot poisoning - contaminated bread) to a deliberate and intentionally conducted experiment to test how LSD affects people on a more massive scale, involving CIA agents (the infamous Project MKUltra https://en.wikipedia.org/wiki/Project_MKUltra
). Other theories include mercury, mycotoxins, or nitrogen trichloride.
Now, even though it is tempting to speculate how the bread got contaminated – by accident or by intention, what I find more relevant (for now) are the consequences and the symptoms. Psychosis is an abnormal condition of the mind, which results in the inability to make a difference between what is real and what is not. Symptoms include hallucinations and delusions (seeing and/or hearing) things that are not present, incoherent speech, illogical decision-making, constant change of moods, false beliefs, and such. One of the ways psychosis may occur is because of ergot poisoning, which is the most credited theory for the accident in France – people ate bread made from rye grain that was infected with the fungus. The victims appeared to have one common connection - they had eaten bread from the bakery of a man named Roch Briand, who was subsequently blamed for using flour made from contaminated rye.
The physical symptoms in the beginning were typical for food poisoning – sore stomach, vomiting, but then it became worse - extreme tiredness and insomnia. For some patients, the symptoms subsided completely for 48 hours, only to return again much worse than before, culminating in vivid hallucinatory episodes involving fire and multi-coloured animals. A number of accounts noted some increasingly bizarre events: man shouting to his room-mates “I’m dead! My head is made of copper and I have snakes in my stomach!”, young girl believe that she was being attacked by tigers, an 11-year-old boy who tried to strangle his mother, a man jumped from the second floor of the hospital, believing he was an airplane, breaking his leg, and then continue to run for 50 meters before being caught by hospital personal. Others could hear celestial harmonies in their heads, and so on.
The whole ordeal lasted for about a week. People were affected in different ways, but the symptoms were pointing to ergot poisoning, even though such cases in France didn’t happen since the 18 century. On the other hand, it coincides with the development of LSD by Albert Hoffman in Sandoz laboratories in Switzerland, which is basically synthesized from the ergot fungus. Hofmann himself first considered that the synthetic drug poisoning was a possibility but he rejected the theory shortly after. Meanwhile, an American laboratory carried out tests on bread deliberately tainted with ergot but noted that volunteers who ingested it “had none of the symptoms reported by victims in Pont-Saint-Esprit.” … So that is the convenient base of the conspiracy theory.
Not surprisingly, there is no official satisfactory explanation for the event.