Is there a SECOND Mona Lisa? Experts examine claims a version of the da Vinci masterpiece is held in a private Russian collection 

Original? The Mona Lisa sits in the Louvre museum in Paris, while a potential second version is held in a Russian private collection

Art experts are examining a painting held in a private collection in St Petersburg they believe might be a second version of Leonardo da Vinci's Mona Lisa.

And leading Mona Lisa scholars say the similarities in colours, which are being examined using infra-red technology, hold the key to determining if the Russian painting is in fact another da Vinci.

'There are many indicators pointing to the Tuscan artistic genius,' research coordinator Silvano Vinceti told ANSA.

'But of course it's only a hypothesis.'  

There are numerous theories that da Vinci painted more than one version and there are conflicting dates about when the painting was commissioned and finished.

New art analysis software, developed by leading da Vinci scholar Carlo Pedretti, has shown that the same artist may have created both the Mona Lisa and the painting in Russia. 

'When comparing the preparatory study from the Louvre and the Russian painting, the overlap between the two was clear to see,' Mr Pedretti said.

'[It's clear from] the columns, present in the Russian painting and in the preparatory study, but also in the perfect resemblance between the upper lip in the preparatory study, the Russian painting and the Mona Lisa in the Louvre.'

Expert restorer of da Vinci's work Paulo De Serra told Italian press that there is a 'possibility the painting could be the work of Leonardo or one of his pupils'. 

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A new BBC2 documentary called 'Secrets of the Mona Lisa,' explored some of these mysteries using new research and technology last week.

Da Vinci is believed to have worked on the painting between 1503 and 1517 and for centuries, it has been believed the woman with the enigmatic smile is Lisa del Giocondo, the wife of a Florentine silk merchant.

Presented by art historian, Andrew Graham-Dixon, the programme used the latest optical, forensic and historical tools to examine new evidence that the painting hanging in the Louvre may not be the original Lisa.

One of the techniques used was the Layer Amplification Method, (LAM) which involves projecting a 'series of intense lights' on a painting to reveal what lies beneath what is visible to the naked eye, the BBC reported. 

Technology: Optical and forensic tools are being used to peel back the truth behind one the world's most famous paintings

It was pioneered by Mr Cotte, founder of Lumiere Technology, who in 2004 was granted access to scan the Mona Lisa and finished the project in 2012. 

A camera is used to project 13 different wavelengths of colour onto a picture, each penetrating the paint surface to different depths.

It then measures the light reflected by these layers, generating over three billion bits of data and thousands of images.

From that data, a reconstruction of what's in between layers of paint can be made.

Mr Cotte claims his technique is able to find layers undetected by other tests.

In a previous study, Mr Cotte worked with academics from French universities to reveal the original colours the Mona Lisa had been after it had been painted. He has also used the technique to study the 'smoky' sfumato style used to achieve the paintings enigmatic smile.