Historians think Lisa Gherardini Del Giocondo, who died in Florence in 1542, modeled for Leonardo's celebrated portrait, now hanging in the Louvre in Paris, ANSA reported.
In a project overseen by Tuscany's Archaeological Ministry, diggers are working in the church of the former convent of St. Ursula using light, low-impact tools such as shovels, trowels, rakes, brushes and sometimes just hands, the Italian news agency said.
Archaeologists were led to the site by references in historical documents and by georadar scans.
"The finding is consistent with our records," art historian Silvano Vinceti, a spokesman for the dig, said. "We should be where the altar once stood, and where a trapdoor led to the crypt we saw on the georadar scan."
The goal of the dig is to find Del Giocondo's remains and compare her DNA with that of two of her children buried in Florence's Santissima Annunziata church. Then, they will reconstruct her face from the skull and compare it to Leonardo's painting.
Del Giocondo became a nun after her husband's death and died in the convent on July 15, 1542, at age 63.