In 1951 a quiet village in southern France was suddenly and mysteriously struck down with mass insanity and hallucinations.

At least five people died, dozens were committed to asylums and hundreds afflicted.

For decades it was assumed that the local bread had been unwittingly poisoned with a psychedelic mould. Now an even more extraordinary explanation has emerged, with evidence suggesting the CIA peppered food with the hallucinogenic drug LSD as part of a mind-control experiment at the height of the Cold War.

The mystery of Le Pain Maudit ("The Cursed Bread") still haunts Pont-Saint-Esprit, in the Gard, south-east France. On August 16, 1951, the inhabitants suddenly suffered frightful hallucinations of terrifying beasts and fire.

One man tried to drown himself, screaming his belly was being eaten by snakes. An 11-year-old tried to strangle his grandmother. Another man shouted, "I am a plane," before jumping out of a second-floor window, breaking his legs. He then got up and carried on for 45 metres. Another saw his heart escaping through his feet and begged a doctor to put it back. Many were taken to the asylum in straitjackets.

Time magazine wrote at the time: "Among the stricken, delirium rose: patients thrashed wildly on their beds, screaming that red flowers were blossoming from their bodies, that their heads had turned to molten lead."

Eventually, it was determined that a baker had unwittingly contaminated his flour with ergot, a hallucinogenic mould that infects rye grain. Another theory was that the bread had been poisoned with mercury.

However, H.P. Albarelli jnr, an investigative journalist, claims the outbreak resulted from a covert experiment directed by the CIA and the U.S. army's top-secret Special Operations Division at Fort Detrick, Maryland.

The scientists who produced both the theories of accidental poisoning, he writes, worked for the Swiss-based Sandoz Pharmaceutical Company, which was then secretly supplying the U.S. Army and CIA with LSD.

Mr Albarelli came across CIA documents while investigating the suicide of Frank Olson, a biochemist working for the Special Operations Division who fell from a 13th floor window two years after the cursed bread incident. One note transcribes a conversation between a CIA agent and a Sandoz official who mentions the "secret of Pont-Saint-Esprit," and explains that it was not "at all," caused by mould but by diethylamide, the D in LSD.

While compiling his book, "A Terrible Mistake: The Murder of Frank Olson and the CIA's Secret Cold War Experiments," Albarelli spoke to former colleagues of Olson, two of whom told him that the Pont-Saint-Esprit incident was part of a mind-control experiment run by the CIA and the U.S. army.

During the 1950s, the U.S. launched a vast research program into the mental manipulation of prisoners and enemy troops.

Scientists at Fort Detrick told him that agents had sprayed LSD into the air and also contaminated "local food products."

Albarelli said the "smoking gun," was a White House document sent to members of the Rockefeller commission formed in 1975 to investigate CIA abuses. It contained the names of French citizens who had been secretly employed by the CIA and made direct reference to the "Pont St. Esprit incident."

In its quest to research LSD as an offensive weapon, Albarelli says, the army also drugged more than 5,700 unwitting U.S. servicemen between 1953 and 1965.

None of his sources would say if the French secret services were aware of the alleged operation.

People in Pont-Saint-Esprit still want to know why they were hit by such apocalyptic scenes.

"At the time people brought up the theory of an experiment aimed at controlling a popular revolt," said Charles Granjoh, 71.

"I almost kicked the bucket," he told a French magazine. "I'd like to know why."