Renaissance artist Leonardo da Vinci did paint an earlier and much younger version of his master-piece Mona Lisa, experts have confirmed.
Art experts claim that Isleworth Mona Lisa, unearthed last year, which shows a significantly younger subject, may be several years older than its more famous counterpart.
Mona Lisa, which has been on display in the Louvre in Paris for three centuries, has long been regarded as the only one painted by the Italian artist, the 'Daily Mail' reported.
However, according to a Swiss-based art foundation, recent tests have shown that the Isleworth Mona Lisa is almost certainly the genius da Vinci's work.
Carbon dating placed the creation of the painting in the correct era, refuting claims that it was a later copy of the main painting, which was created in around 1516.
Geometric analysis has shown that painting matches the proportions da Vinci depicted in his human forms.
The results may help convince other experts who were sceptical when the painting was unveiled in Geneva last year, after it had been kept in a Swiss bank vault for four decades.
The international group claimed that its authenticity has finally been proven.
"When we add these new findings to the wealth of scientific and physical studies we already had, I believe anyone will find the evidence of a Leonardo attribution overwhelming," David Feldman, vice-president of the foundation said.
Feldman said he was contacted after the public unveiling of the portrait by Italian geometrist Alfonso Rubino.
"He has made extended studies of the geometry of Leonardo's Vitruvian Man (a sketch of a youth with arms and legs extended) and offered to look at our painting to see if it conformed," he said.
Rubino said that the "Isleworth" portrait - named after a London suburb where it was kept by British art connoisseur Hugh Blaker 80-90 years ago - matched da Vinci's geometry and must be his, the report said.
The Zurich institute carried out a carbon-dating test on the canvas of its painting and found that it was almost certainly manufactured between 1410 and 1455 - refuting claims that it was a late 16th century copy, the Foundation added.
Supporters of the 'younger' version say the portrait was almost certainly delivered unfinished to del Giacondo before Leonardo left Italy in 1506 and took up residence in France, where he died in 1519 in a small Loire chateau.