A stranger presented the 19th century painting by Jean Leon Gerome to Communist Party leader Gennady Zyuganov in his office, the party said earlier.
Anatoly Vilkov, the deputy head of the federal media and cultural heritage agency, said agency experts had "established the authenticity of the painting. As well as the genuine brushwork of the artist, there were signs that enabled them to identify it."
The Communist leader said earlier that the painting had been sliced up, and was in terrible condition.
Vilkov said the work of art had probably been handed in by a Communist Party sympathizer.
"It was probably a spontaneous theft, and then the painting went from hand to hand," he said.
Leon Gerome's 'Piscine du Harem' (Harem Pool), painted in 1878 and measuring 73.2 x 62 cm, was bought into Russia by Emperor Alexander III. Its value is estimated at $1 million.
The Communist leader identified the painting after finding an official statement by the Hermitage administration saying an unidentified person had cut the picture out of its frame and stolen it on March 22, 2001.
Specialists from the agency have put the painting in special storage where they are continuing to work on the canvas. Despite severe damage, the work can still be restored, Zyuganov said.
