PARIS -- A nude drawing that bears a striking resemblance to the "Mona Lisa" was done in Leonardo da Vinci's studio and may be the work of the master himself, a French museum said Monday.

Experts at the Louvre in Paris, where the world's biggest collection of Leonardo's work is held, have been examining a charcoal drawing known as the "Monna Vanna" which has long been attributed to the Renaissance painter's studio.

But the charcoal preparatory work for a painting of a semi-nude woman, held at the Conde Museum at Chantilly north of Paris, may now have to be reclassified.

"There is a very strong possibility that Leonardo did most of the drawing," Mathieu Deldicque, a curator at the Paris museum, told AFP.

"It is a work of very great quality done by a great artist," added Deldicque, who initiated a investigation over several months by historians and scientific specialists at the renowned C2RMF laboratory under the Louvre.

The large drawing has been held since 1862 in the huge collection of Renaissance art at the Conde Museum, once the home of one of France's oldest noble families.

"It is almost certainly a preparatory work for an oil painting," Deldicque said, with the hands and body almost identical to the "Mona Lisa," Leonardo's inscrutable masterpiece which hangs in the Louvre.

Exceptional artist

Microscopic examinations have shown that it was drawn from the top left towards the bottom right, the curator said -- which points to a left-handed artist.

Leonardo, who died in France in 1519, is the most famous left-handed painter in history.

The drawing will be shown at a special exhibition at Chantilly later this year to mark the 500th anniversary of the death of the artistic genius, who was born in the Medici-ruled Republic of Florence in 1452.

Louvre conservation expert Bruno Mottin had earlier confirmed that the work dated from Leonardo's lifetime.

But he was thrown by "hatching on the top of the drawing near the head done by a right-handed person."

Since then "we have discovered lots of new elements," Deldicque said, most notably "left-handed charcoal marks pretty much everywhere."

Tests had already revealed that the drawing on paper, using Leonard's beloved "sfumato" technique, was not a mere copy of a lost original.

But Deldicque said that "we must remain prudent" about definitively attributing the work to the great polymath.

"We want to be serious and scientific about this," he told AFP. "The quality of the drawing, both to the naked eye and under imaging analysis" shows it was the work of an exceptional hand.

But experts cannot be "absolutely certain (it was by Leonardo) and we may never be," he admitted.

© Agence France-Presse