Paris' Musee d'Orsay have confirmed its authenticity, but its not known why the painting was on the bus or who left it there.
ADVERTISEMENTA stolen painting by 19th century Impressionist master Edgar Degas has been found by French customs in a suitcase in a bus' luggage compartment.
The 1877 piece called "Les Choristes" (The Chorus Singers) was stolen nine years ago from the Cantini museum in Marseille when it was loaned for a temporary exhibit by Paris' Musee d'Orsay.
The work, done in pastel, depicts a line of men singing in the opera Don Juan.
Police were making random checks on a bus at a highway rest area about 30 kilometers east of Paris when they found it.
The French Culture Ministry says none of the bus passengers claimed the suitcase during the Feb. 16 search.
The French artist is most famous for his paintings and sculptures of dancers and is often associated with the Impressionist movement.
France's Culture Minister Francoise Nyssen said she was delighted with "this happy rediscovery... whose disappearance represented a heavy loss for the French impressionist heritage."