The German government says it is helping Bavarian prosecutors investigate a huge art find related to pieces seized by the Nazis from Jews and art that the Nazis considered "degenerate."

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. The estimated value of the works is approximately €1 billion (about $1.4 billion Cdn).

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."

According to local reports, police discovered the works during a raid of a house of a recluse who was suspected of tax evasion and whose father was an art dealer. Investigators say there are international warrants active for approximately 200 of the paintings.

Over the past decade, the worldwide art community has increasingly opened up to returning Nazi-looted art to rightful heirs.

Last week, following an intensive survey, Dutch museums identified 139 artworks in their collections — including paintings by French master Henri Matisse and Dutch impressionist Isaac Israels — that have dubious provenance and were likely snatched forcibly from Jewish owners during the Nazi regime.

Nazi-looted art seized

A German newspaper announcing a "Billion Euro Art Treasure Discovered In Schwabing" is displayed in front of the Munich apartment building where, according to media reports, officials seized 1,500 paintings believed confiscated by the Nazis in the 1930s and 40s. (Lennart Preiss/Getty Images)