After 10 years of detective work, the Minneapolis Institute of Arts has concluded that a $2.8 million painting it has owned for decades was stolen by the Nazis. The museum has returned the 1911 painting, Fernand Leger's "Smoke Over Rooftops," to the French heirs of a Jewish art collector who died in 1948. The institute's saga began in 1997 when the museum received a letter claiming that the painting had been taken from Alphonse Kann, a legendary French art collector who owned "tons of Picassos, Braques and late-19th-century Impressionist paintings." His story helped inspire a 1964 movie, "The Train," starring Burt Lancaster, about a trainload of art that the Germans tried to spirit away before the Allies liberated Paris in 1944. Much of Kann's art was returned to him after World War II, but not the Leger. That painting was bequeathed to the museum in 1961 by a Minneapolis businessman who bought it from the Buchholz Art Gallery in New York in 1951. No one questioned the picture's history. Nazi-era archives were sealed in France and inaccessible in Soviet-controlled Eastern Europe. Responding to the claim took years because the museum had to establish if it was legitimate. Was this Leger the same one Kann had owned? ("Smoke Over Rooftops" was a theme Leger painted at least six times.) If so, what had happened to the picture between 1939, when Kann fled Paris on the eve of war, and 1949 when a New York art dealer bought it from a French gallery? Did Kann sell it freely, or did the Nazis confiscate it? "Many of the people who could tell stories and remember what happened were gone," Not until the Soviet Union dissolved in 1991 did people began to grapple seriously with the fallout of the Nazi practice of confiscating art from Jewish collectors or forcing them to sell it under unconscionable circumstances. At that point museums realized they had to "do the right thing," which often meant returning the art to heirs, even if the art had been acquired innocently. Resolution of the Leger painting's fate required a French lawsuit and years of painstaking scrutiny of Nazi-era documents, gallery and auction records in four countries. The research established that, after Kann fled to London, the Nazis confiscated the bulk of his collection and in 1940 moved it to the Jeu de Paume, a museum in central Paris, where it was inventoried and stayed during most of the war. The art collection was so extensive that the Nazis' list ran to 60 typed pages. The Leger painting, however, remained in Kann's house until Nov. 5, 1942, when France's German-controlled government auctioned the house's contents. A Paris art dealer, Galerie Leiris, bought the Leger at that auction and subsequently sold it to Buchholz Gallery. Leiris was essentially a front for a prominent German-Jewish art dealer, Daniel-Henry Kahnweiler, who had transferred title to his business to his French Catholic sister-in-law, Louise Leiris, when the Nazis moved in and threatened to confiscate his company. Buchholz Gallery was established in the 1930s by Curt Valentin, a protege of a Berlin art dealer, Karl Buchholz, who was one of four German art dealers whom the Nazis allowed to sell the modern art they confiscated from museums and private collectors. While Valentin has not been implicated in the Nazis' nefarious deeds, his role in the transfer of modern art out of Europe is ambiguous at best. Making matters more difficult, the current owners of Galerie Leiris refused to open its archives until forced to do so by a 2001 lawsuit in a different case. Settling such claims is expensive. The Minneapolis museum hired art scholars in Paris and London, corresponded with bureaucrats in Germany and studied archives in New York, Los Angeles and Washington. What will happen to the Leger painting now is unclear. No one from the French collector's family could be reached for comment. Initially the museum hoped Kann's heirs would lend or give it to the museum but that proved impossible. Asked if the institute would try to buy it back if the Leger were to be offered at auction, the museum made clear they had "..two other very nice Leger paintings in the art collection."