As researchers dig deeper into the activities of French institutions during the dark time of the German Occupation in World War II, ever more art controversies are coming to light. During the war, thousands of artworks moved through the former Musée du Jeu de Paume (or Tennis Court Museum) after being confiscated from Jewish dealers and collectors with the help of the Gestapo and the Commissariat for Jewish Questions. We now know that this is what happened to three paintings by artist Fédor Löwenstein that ended up in the permanent collection of the Pompidou Center.

According to Rue89, the Pompidou Center has admitted that "Les Peupliers (Poplars)," "Arbres (Trees)," and "Composition" were originally pillaged by the Nazis. Alain Prévet, head of the Archives of French National Museums, and Thierry Bajou, head conservator for the National Heritage of French Museums, made the discovery after studying the invaluable archives of Rose Valland, a conservator at the Jeu de Paume who single-handedly kept track of the art crimes perpetrated by the Nazis at the museum during the Occupation. Valland's records have allowed numerous artworks to be returned to their rightful heirs.

Over the course of the Occupation, Hitler and Göring selected artworks that they liked and had them sent back to Germany, destined for their personal collections, to be given as gifts to high-ranking Nazis, or to be sold on the black market. In 1942, Valland noted that several works that were "not in keeping with the aesthetic of the Third Reich" were stored separately in the museum's so-called "Martyrs Room." Valland listed six works by Löwenstein that were held there.

After the Liberation, the Einsatzstab Reichleiter Rosenberg, which had been in charge of confiscating "degenerate" or "Jewish-influenced" art, left behind a handful of photographic negatives of the Marytrs Room. Prévet and Bajou digitized the images and enlarged them, comparing what they saw with Valland's inventory. This allowed them to identify 60 paintings, including two by Löwenstein. When they entered the artist's name into the Pompidou Center's collection database, three works came up, all ostensibly donated in a mysterious gift to the museum in 1973.

Working with the Pompidou Center, the team discovered that the leadership of the museum, unable to account for the Löwenstein paintings, simply transformed them into gifts in order to establish a provenance for the works in their inventory. The paintings have now been removed from that inventory and put on a list of stolen works maintained by the Musées Nationaux Récupération project. The next step is to find the rightful heirs.

This restitution case is far from the first to arise in European museums. Last April, the Museum der Moderne in Salzburg had to return Gustave Klimt's "Litzlberg am Attersee," which had been stolen from Amalie Redlich, a collector who died after being deported to a Polish ghetto. Her sole heir has since sold the painting, which fetched $40.4 million at a Sotheby's auction last month. In October, a casino in southern Germany returned a work by Juriaen Pool the Younger to three universities who were the beneficiaries of art dealer Max Stern's will. The universities decided to donate the piece to the Amsterdam Museum.

In yet another recent case, Zürich's Kunsthaus acknowledged that "Madame Le Suire" by Albert von Keller had been pilfered by the Nazis, but the rightful owner's heirs offered to donate the work to the museum on one condition — that the painting be displayed with the following information: "Stolen from Alfred Sommerguth in 1939 by the Nazis. Gift of his heirs and of Mrs. Hannelore Müller in 2010."