In 1940, the Nazis seized a Claude Monet pastel and seven other works of art from Adalbert "Bela" and Hilda Parlagi, a Jewish couple forced to flee their Vienna home after Austria was annexed into Adolf Hitler's Germany.

The family recovered another work in March from the Austrian government but there are still six more artworks missing, including from acclaimed artists Camille Pissarro and Paul Signac. The U.S. is likely the “largest illegal art market in the world,” said Kristin Koch, supervisory special agent with the FBI's Art Crime Program.