It was initially thought that the local baker had unwittingly baked some ergot-infected wheat into bread, which was consumed by the locals. The villagers would then have been victims of ergot poisoning, or St. Anthony's Fire--a very not-pleasant combination of hallucinations and convulsions. In extreme cases, gangrene in the limbs develops and death can occur.
New evidence has allegedly come to light now, whereby it's being claimed that there's documentation to show that CIA agents, working in conjunction with some scientists at the Sandoz Laboratories (where LSD was first synthesized), conspired with a few French 'plants' to essentially dose the population with LSD and observe the results. What swell critters, eh?
It definitely seems plausible, given the agency's track record with other experiments of a similar nature. What amazes me is how long it took for the original files to be made public. I suppose it shows a sliver of progress that the Iran-Contra affair was exposed after only a few years of being in operation. Same old CIA. Robert Anton Wilson once quipped that if the gubberment were really fighting a 'war on terror', they would carpet-bomb Langley, Virginia. But of course, like the 'Drug War', it's only a war on some terrorists (mostly brown ones, with funny names, who don't worship the X-tian 'God').
Now, if I lived in a paranoid reality-tunnel most of the time - I'd ask why the Pont-Saint-Esprit story is surfacing now. I'd think that maybe it's another scare-story about psychedelics, to try and put the kibosh on any legitimate research. The Beckley Foundation is starting a research project on LSD and I suspect that M.A.P.S. will be soon, too. Ah well, hopefully humans have learned more and got a bit smarter since psychedelics were demonised by the mainstream press in the 1960s. I say hopefully....
Here's a great little film showing LSD experiments with British soldiers in the early 1960s: