In a story that has rocked the art world, a Michelangelo original may have been discovered in the most unlikely of locations - the lounge of a private house in the US city of Buffalo.

American cities are not noted as a repository for undiscovered works by the Great Masters, so many experts are cynical of the "find".

Rather than hanging on a museum wall, the unfinished painting, featuring Virgin Mary cradling the body of Jesus, was for years stuffed behind a sofa in the house of the Kober family.

Even the Kobers, who took the picture off their wall after it was hit by an errant tennis ball, weren't sure whether it was priceless or worthless.

If it is a Michelangelo, it is considerably closer to the former than the latter, and, if similar works at New York's Metropolitan Museum of Art are any guide, could be worth anything up to $300m.

The quest to find out the truth was started, on his father's urging, by Lieutenant Colonel Martin Kober in 2003 after his retirement from the US Air Force. He took his job seriously, vaguely conscious that the bundle behind the couch might one day become the most important art find of the century.

He contacted auction houses, art historians and even visited a leading expert on Michelangelo in Italy, Antonio Forcellino.

For Mr Forcellino the visit by Lt. Col Kober marked the beginning of an unexpected adventure. He was sceptical at first that the 19x25-inch painting on wood which the Kobers had half-jokingly christened the "Mike" could be the real thing.

Mr Forcellino's research - outlined in his new book, La Piet Perduta (The Lost Pieta) - points to the picture being by the master. Michelangelo's 1499 sculpture masterpiece, Piet, is housed at St Peter's Basilica in the Vatican.

"I'm absolutely convinced that is a Michelangelo painting," Mr Forcellino told the New York Post.

"In reality, this painting was even more beautiful than the versions hanging in Rome and Florence. I had visions of telling them that there was this crazy guy in America telling everyone he had a Michelangelo."

Part of what helped to convince him was the result of X-ray and infrared examinations of the painting which reveal multiple alterations, not something you would expect in a copy of an original, as well as an unfinished section near the Madonna's right knee. By tracking the provenance of the work he was also able to work out how it ended up in Buffalo.

Mr Forcellino believes the work was painted by Michelangelo, in about 1545, as a gift for a friend. It then passed to two Catholic cardinals before ending up in the hands of a German baroness. She bequeathed it to a favourite lady-in-waiting who was the sister-in-law of Mr Kober's great grandfather.

Definitive proof that this work was by the brush of Michelangelo may be hard to come by, but if sufficient numbers of experts agree with Mr Forcellino that should be enough to make the Kobers very wealthy indeed.

Buffalo residents (and the rest of us) will meanwhile have to remain patient.

The picture is not on public display in the Kober home or anywhere else. They have it stashed away - not behind the family furniture any more, but in the vault of a bank.