The 1877 monotype “Les Choristes” (The Chorus Singers) by Edgar Degas is distinctive for at least two reasons.

First, the French impressionist depicted dancers so often that this work is his only operatic scene to omit them.

Second, it was stolen in a mysterious December 2009 heist after thieves unscrewed it from the wall one night at Musée Cantini in Marseille, leading investigators to speculate that the theft could be an inside job.

The trail had grown cold over the years, as French customs investigators tried in vain to find the artwork, valued at more than $1 million. Yet on Feb. 16, it was not discovered at a shady auction house or the vault of an art thief, but inside a suitcase in the back of a bus at a highway stop near Paris.

Customs officials were performing a random search of the bus luggage compartment when they found a suitcase containing the work, bursting with vivid pastel hues of orange, yellow and red, depicting chorus singers in the opera “Don Juan.”

The bus was parked near Ferrières-en-Brie, a verdant area about 18 miles east of Paris. None of the passengers claimed the suitcase as their own, according to France's Ministry of Culture. A customs spokesman said the find was not based on a tip, the New York Times reported. Long-distance buses in many countries, including France, are often searched for drugs.

The painting was confirmed as authentic by Musée d'Orsay, the museum that loaned it to Cantini. Minister of Culture Françoise Nyssen called its recovery a “happy rediscovery” of the work. Its disappearance “represented a heavy loss for the French impressionist heritage,” Nyssen said.

Degas's work is known as a monotype, or a cross between a painting and engraving. An artist creates an ink composition and brushes it on a metal plate before pressing it, the Culture Ministry said.

The find comes at a serendipitous moment, the ministry notes. Degas died a century ago this past September, and an exhibit featuring the friendship between him and the French poet Paul Valéry wraps up on Sunday at Musée d'Orsay. The monotype also will be featured at a Degas exhibit opening next year.

While the recovery of the Degas is notable, French customs agents seized more than 10,000 works of art in 2016, mostly coins and archaeological objects, including marble works from the 14th and 16th centuries they said were looted during the Syrian war.

In 2015, customs intercepted a private yacht in the Mediterranean displaying a painting by Pablo Picasso forbidden from leaving Spain. It was bound for sale in Switzerland, according to a tip. The painting was returned to Spain, Picasso's home country.

Read more: