Tomb opened in search for identity of Mona Lisa

Researchers opened a centuries-old Florence tomb on Friday in a search for remains that could confirm the identity of the woman whose enigmatic smile Leonardo da Vinci immortalized in the "Mona Lisa", one of the world's most famous paintings.

The tomb contains the family of Lisa Gherardini, the wife of a silk merchant, who is believed to have sat for the artist.

It is hoped DNA will help to identify her from three skeletons found last year in a nearby convent.

Experts have for centuries puzzled over the woman featured in the Mona Lisa.

To find the DNA they needed, scientists cut a round hole in the stone church floor above the family crypt of Florentine silk merchant Francesco del Giocondo. The tomb lies behind the altar of the Santissima Annunziata Basilica.

Writer and researcher Silvano Vinceti plans to compare DNA from the bones with that of three women buried at the nearby convent of Saint Ursula. Lisa Gherardini died there as a nun in 1542

It is hoped that some of the bones will belong to at least one of her blood relation, probably her son, Piero.

"When we find a match between mother and child - then we will have found the Mona Lisa," Vinceti said.

He added that once a DNA match is made, an image of Gherardini's face can be generated from the skull and compared with the painting.

Leonardo da Vinci took about 15 years to complete what has become one of the most famous paintings of all time. After Leonardo's death, it was acquired by the King of France.

The painting, which draws millions of visitors each year, is famous for the sitter's mysterious half-smile. The Louvre says it was probably painted between 1503 and 1506.

Opening the Giocondo family tomb for the first time in 300 years is a critical phase in the search by Vinceti and his team, who in 2010 said they had discovered that the mysterious death in 1610 of another Italian master, Caravaggio, was likely caused by lead from his paint.

The researchers say carbon-dating tests on three of eight skeletons exhumed from the Saint Orsola convent are under way and they will do the same with the contents of the Giocondo tomb - although it could take a year before the DNA testing process is started.

Leonardo is famous for the huge range of his genius, ranging from painting to sculpture to anatomy. He is known not only for paintings like the "Mona Lisa" and "The Last Supper", but for conceiving modern machines like helicopters and tanks many centuries before they were finally built.