Story highlights Unknown works by Matisse and Chagall among haul found in Munich apartment

Treasure trove of paintings was discovered in raid by German tax authorities

Pieces by Picasso, Toulouse-Lautrec, Dix, Renoir, Courbet and Canaletto also recovered

Experts say many of the works are so called 'Degenerate Art' confiscated by Nazis

(CNN) Previously unknown paintings by Henri Matisse, Marc Chagall and Otto Dix are among a treasure trove of art -- much of it believed to have been looted by the Nazis -- found hidden in a Munich apartment.

The vast collection, which experts say has "a value so high it cannot be estimated," was recovered in a raid by German tax authorities, in connection with an investigation into tax evasion, in February and March 2012.

At a press conference in Germany on Tuesday, experts revealed that more than 1,300 artworks -- many long feared lost or destroyed, and some which had never been recorded -- had been discovered.

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Among the haul were paintings by Pablo Picasso, Henri de Toulouse-Lautrec, Oskar Kokoschka, Canaletto, Pierre-August Renoir, Franz Marc and Gustav Courbet.

"A total of 121 framed and 1,285 unframed works, among them works by famous artists, were seized," prosecutor Reinhard Nemetz announced. "There were oil paintings, works in india ink, pencil, watercolors, lithographs and prints."

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