Francoise Nyssen said customs officials found the pastel -- thought to be worth around 800,000 euros ($893,000) -- hidden in the luggage compartment of a bus stopped in a motorway layby.
![Linn of Tummel Waterfall [UKNIP]](data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20width%3D'100'%20height%3D'100'%20data-ring-placeholder%3D'1'%3E%3C%2Fsvg%3E "Linn of Tummel Waterfall [UKNIP]")
None of the passengers on the bus admitted to knowing anything about the painting, she added.
Experts from the Musee d'Orsay in the French capital later confirmed that the depiction of a group of opera extras was "Les Choristes" -- sometimes called "The Extras" -- which was stolen in 2009 from the Musee Cantini in the southern port city.
It was the only time non-dancers ever appeared in the aristocratic ballet-loving artist's work inspired by life at the opera.
Degas was at the height of his powers when he created the piece in 1877, just before his sight began to decline.
The confirmation of the find comes as a major exhibition about the artist's relationship with the dancers at the Paris Opera closes at the Musee d'Orsay this weekend after attracting nearly half a million visitors.
'Wonderful happy ending'
"It is a wonderful happy ending to the story," said a spokeswoman for the museum, which holds the world's largest collection of Impressionist art.
"It is the centenary of his death, and we are organising a huge show about Degas and the opera for 2019. It would have been a terrible loss for us to do it without this painting," she told AFP.
Nyssen said that the painting -- which shows a scene from "Don Juan" -- will now have a "special place" in the "Degas at the Opera" show, which will open in September 2019.
The painting mysteriously disappeared from the Marseille museum on New Year's Eve 2009. It was on loan from the Musee d'Orsay for an exhibition on art and theatre.
The police's specialist anti-art crime unit said there had been no trace of the painting during the intervening years.
Nyssen said paid tribute to the customs officials who made this "happy discovery" and said the theft had been "a major loss from France's Impressionist heritage."
Gerald Darmanin, the French minister in charge of the customs service, refused to reveal how the recovery was made, but said that officers were on high alert over the smuggling of stolen or looted artworks and historical artefacts.
He said France had returned eight 3,000-year-old Egyptian antiquities to Cairo that customs officers found in the baggage of a British man at a Paris railway station in October.
He said they were watching out particularly for treasures which had been pillaged from war-torn Syria.
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![The woman was recorded, among others, while bathing [BI]](data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20width%3D'300'%20height%3D'172'%20data-ring-placeholder%3D'1'%3E%3C%2Fsvg%3E "The woman was recorded, among others, while bathing [BI]")
