PARIS – A rib bone supposedly found at the site where French heroine Joan of Arc was burned at the stake is actually that of an Egyptian mummy, according to researchers who used high-tech science to expose the fake.

The bone, a piece of cloth and a cat femur were said to have been recovered after the 19-year-old was burned in 1431 in the town of Rouen. In 1909 – the year Joan of Arc was beatified – scientists declared it “highly probable” that the relics were hers.

But starting last year, 20 researchers from France, Switzerland and Benin took another look. Even they were surprised to find the rib bone came from an Egyptian mummy. Their best guess is that the fake was cooked up in the 19th century, perhaps to boost the process of Joan of Arc’s beatification. She was canonized as a saint in 1920 by the Roman Catholic Church.

In medieval times and later, powdered mummy remains were used as medicine “to treat stomach ailments, long or painful periods, all blood problems,” said Philippe Charlier, who headed the research team.

The team’s assumption is that a 19th-century apothecary transformed “these remains of an Egyptian mummy into a fake relic, or fake historic remains, of Joan of Arc,” he said.

Tests dated the rib bone to between the 7th and 3rd centuries B.C., he said. The cat bone dated from the same period and also was mummified. The researchers also found pine pollen, probably from resin used in Egyptian embalming, he said.

They were unable to extract DNA from the remains, meaning they could not identify the sex of the mummy or the cat.

Even perfumers were called in as detectives. The researchers had them sniff the remains, using their exceptional olfactory senses “so they could identify the smells, the vegetable matter, in the embalming and guide our research,” Charlier said.

Joan of Arc was tried for heresy and witchcraft and executed after leading the French to several victories over the English during the Hundred Years War, notably in Orleans, south of Paris.

The journal Nature was first to report that the team had concluded that the bone was from a mummy, not Joan of Arc.