ROME (AP) — Art experts have confirmed that a stolen painting discovered hidden inside an Italian art gallery's walls is Gustav Klimt's "Portrait of a Lady," Italian prosecutors said Friday.

A gardener reported finding an art work inside a bag last month while clearing ivy at the Ricci Oddi Modern Art Gallery in the northern city of Piacenza. “Portrait of a Lady” disappeared from the gallery during renovation work in February 1997.

"It's with no small emotion that I can tell you the work is authentic," Piacenza Prosecutor Ornella Chicca told reporters at a news conference.

The portrait, of a young woman sensually glancing over her shoulder against a dreamy green background, was displayed on an easel and flanked by two police officers during the announcement.

The painting is a later work by the Austrian art nouveau master. Klimt painted it in 1916-17, and its disappearance had been one of the art world's biggest mysteries.

There had been widespread optimism in Italian art circles that the gardener's discovery would turn out to be the missing Klimpt. Italy's Piacenza Sera quoted gallery officials as saying the back of the canvas bore stamps that were put on when the painting was on loan.

Since it's discovery, the work had been kept in a vault of a local branch of Italy's central bank.