A Cézanne watercolor recently shown at the Fondation Beyeler in Basel may have been lost by its Jewish owner as a result of Nazi persecution, according to a provenance researcher working for the man’s heir.

The work, La Montagne Sainte Victoire (ca. 1888), appeared in the Beyeler’s recent Cézanne exhibition, which closed Monday. Its lender was identified in the catalogue only as a private collector.

Researcher Willi Korte told the Art Newspaper that he uncovered documents in Basel’s public archives showing that Gustav Schweitzer, a Jewish businessman who fled Berlin in 1935, loaned the watercolor to a 1936 exhibition at the Kunsthalle Basel. Correspondence reviewed by Korte shows that Schweitzer later asked the museum’s curator to keep the watercolor safe after the exhibition and help find a buyer for it. The curator arranged for the work to be restored at Schweitzer’s expense, but after no sale materialized, the watercolor was sent back to Schweitzer’s secretary in Paris in 1939. What happened to the work afterward remains unclear.

Korte argued that the circumstances suggest the work was either sold under duress after Schweitzer fled Germany or looted in Nazi-occupied territory. He urged the Fondation Beyeler not to simply return the work to its lender, saying the museum should help pursue what he called a “fair and just solution.”

The Fondation Beyeler, according to the Art Newspaper,  said it would inform the lender of the claim but return the watercolor, stating that Swiss museums do not have the legal authority to retain works without an appropriate legal basis. The museum also said it is not possible to research the provenance of loans to temporary exhibitions with the same depth as works in its permanent collection. It added that the watercolor was not listed on Germany’s Lost Art Database.

Schweitzer died in Manila in 1939 after leaving Paris on a business trip. His secretary was deported from Paris in 1942 and killed at Auschwitz a week later. Schweitzer’s wife fled to the United States in 1938, and their grandson, who lives in the US, is now the family’s sole heir.

The dispute arrives amid continued scrutiny of Nazi-era provenance research in Switzerland, particularly following debate around the Emil Bührle Collection at the Kunsthaus Zurich. A recent report on the collection examined a Van Gogh once owned by Schweitzer and concluded that a persecution-related loss could not be ruled out.

Historian Georg Kreis, who has served on several panels examining Switzerland’s role during the Nazi era, suggested the Fondation Beyeler could help mediate between Schweitzer’s heir and the work’s current owner. He told the Art Newspaper that the watercolor would likely become difficult to sell under what he called a “heavy cloud of suspicion,” and said any agreement should acknowledge the possibility of a persecution-related loss and compensate Schweitzer’s descendants accordingly.