The experts from Canada's National Research Council said the painting was in fragile condition but should not suffer too much damage if taken care of properly.

"The wood panel on which the Mona Lisa is painted is sensitive to temperature and climate variations. However, if its current storage conditions are maintained, there is no risk of degradation," the NRC said in a statement.

"The 12 cm (3-1/2 inch) split on the top half of the painting, which was probably due to the removal of the original frame and repaired between the middle of the 18th and beginning of the 19th century, appears to be stable and has not worsened over time."

The council had hoped to discover more details about Leonardo's "sfumato" technique of subtly blending one tone into another, which the artist used to create a hazy effect. But scientist John Taylor said the team had been frustrated by the lack of brush stroke detail on the painting.

"It's extremely thinly painted and extremely flat, and yet the details of the curls of hair, for example are extremely distinct. So the technique is unlike anything we've ever seen before. Leonardo was in a league of his own," he said.

Close examination of the craquelure -- the fine pattern of cracks formed on old paintings -- showed the paint layers were still firmly attached to the poplar wood panel on which Leonardo created his masterpiece.

"We didn't see any sign of paint lifting. So for a 500-year-old painting it's very good news. And if they continue to keep it the way they have in an environment-controlled chamber, it could remain like that for a very long time," Taylor said.

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