A nude sketch that bears a striking resemblance to the Mona Lisa may have been drawn by Leonardo da Vinci, experts have said.

Scientists at the Louvre in Paris, where the painting is held, have been examining a charcoal drawing known as the Monna Vanna, which had been attributed to the Florentine master’s studio.

The large drawing has been held since 1862 in the huge collection of Renaissance art at the Conde Museum, in the palace of Chantilly, north of the French capital.

After a month of tests, curators believe the sketch is at least in part by Leonardo. “The drawing has a quality in the way the face and hands are rendered that is truly remarkable. It is not a pale copy,” said curator Mathieu Deldicque.

“We are looking at something which was worked on in parallel with the Mona Lisa at the end of Leonardo’s life. It is almost certainly a preparatory work for an oil painting.”

The hands and body in the sketch were almost identical to that of the Mona Lisa, Deldicque.

The drawing is almost the same size as the Mona Lisa, and small holes pierced around the figure suggest it may have been used to trace its form on to a canvas.

A Louvre conservation expert confirmed the drawing was created during Leonardo’s lifetime at the turn of the 15th century.

Bruno Mottin told the Parisien newspaper tests had revealed the high-quality work was not a copy of a lost original.

He cautioned that “we must remain prudent” about definitively attributing the sketch to Leonardo, who died in Amboise, France, in 1519.

“The hatching on the top of the drawing near the head was done by a right-handed person. Leonardo drew with his left hand. It is job that is going to take some time,” Mottin said. “It is a very difficult drawing to work on because it is particularly fragile.”

But Mottin said they hoped to establish the identity of the artist within two years, in time for an exhibition at Chantilly to celebrate the 500th anniversary of Leonardo’s death.

More than 10 experts have been examining the drawing for the past few weeks, performing scans and using other scientific methods.

Their investigations have centred on working out whether the drawing was made before or after the Mona Lisa, which was painted sometime after 1503.

The Chantilly drawing had originally been attributed to the Tuscan master when it was bought by the Duc d’Aumale in 1862 for 7,000 francs, a substantial sum at the time.

But later specialists had their doubts and thought it probably came from a member of the artist’s studio.

About 20 paintings and drawings of nude Mona Lisas exist in collections across the world but most have proved very difficult to date.