Focus magazine reported Sunday that about 1,500 works by such masters as Pablo Picasso, Henri Matisse and Emil Nolde were found in a Munich apartment in early 2011 but gave no sources for its information.
Bavarian prosecutors declined to confirm or deny the report.
Asked about the Focus report on Monday, German government spokesman Steffen Seibert said authorities in Berlin are aware of the case and are supplying "advice from experts in the field of so-called 'degenerate art' and ... Nazi-looted art."
