Bavarian customs investigators originally found the art in a trash-filled Munich apartment belonging to an 80-year-old man more than two years ago, but it was not disclosed at the time, Focus magazine reported on Sunday.

The stash includes artwork by renowned painters like Pablo Picasso, Henri Matisse, Marc Chagall, Emil Nolde, Franz Marc, Max Beckmann, Paul Klee, Oskar Kokoschka, Ernst Ludwig Kirchner and Max Liebermann. Focus estimated the collection to be worth 1 billion euros ($1.4 billion).

The Nazis confiscated vast quantities of art that during their 1933-45 rule and much of it remains unaccounted for. Jewish art collectors were forced to sell their works at a significantly reduced price, or it was simply confiscated by Nazi censors from galleries for allegedly being "degenerate."

Hidden for more than half a century

According to Focus, the paintings were purchased by art dealer in the 1930s and 40s. They were then passed onto his son, who kept them for more than 50 years in home-made wooden shelves in dirty, darkened rooms. He reportedly lived off money from selling the paintings occasionally.

Authorities caught wind of him when he was caught with undeclared cash while traveling via train from Switzerland to Munich. Further investigation led to a search of his apartment in early 2011.

The works were taken to a secure customs storage depot. Focus said that a Berlin art historian had been hired to investigate art's value and where it came from.

Thousands of artworks taken under duress by the Nazis have been, in accordance with German law, returned to their original owners or their heirs.

But many more have not yet resurfaced. According to recent estimates, tens of thousands of artworks have yet to be restored to their rightful owners.

dr/rc (dpa, AFP)