Is a 16th-century charcoal sketch a naked Mona Lisa?

Art experts are examining a nude sketch as the possible basis for Leonardo da Vinci's Mona Lisa.

CHANTILLY AND PARIS, FRANCE (REUTERS) - Could this be the Mona Lisa in the nude?

According to some experts, it might be.

The charcoal drawing, known as the Monna Vanna, has been kept in a collection for more than 150 years.

It was thought to have been drawn by a student of Leonardo Da Vinci.

But now clues suggest it may be the work of the master himself.

Chantilly museum curator Mathieu Deldicque says: "What is really impressive are the hands, they have the same position as those in the Mona Lisa."

Among the signs - the drawing was made during the same period as the Mona Lisa and the paper is from the same region of Italy.

The technique is also very similar that of the famous masterpiece.

Says Mr Deldicque: "We know that Da Vinci was left-handed, so we're looking for strokes of a left-hander. We haven't found it yet - but there's no evidence that of a right-hander either. It's still a mystery."

Experts will continue analysing the work for another month.

That may still not prove who produced the piece.

But there is excitement just at thought of another Da Vinci legacy.

Mr Deldicque says: "This is why Da Vinci's works are talked about so much - there is always its shadow, a mystery to his works and we're always trying to uncover it."