A haul of Monets, Picassos and Renoirs found last month in a house in Austria belonging to Cornelius Gurlitt could be as valuable as the original trove German authorities seized from his home in Munich two years ago, a spokesman for the reclusive collector said Thursday.

German magazine Focus, which first reported the case, said the Munich find could be worth €1 billion euros ($1.38 billion US). The 1,400 works included paintings by Pablo Picasso, Henri Matisse and Marc Chagall, some of which authorities believe may have been looted from Jewish owners by the Nazis.

"We can't say at this stage which part of the collection is more valuable," Gurlitt's spokesman Stephan Holzinger told The Associated Press, but added that the Focus estimate was "completely exaggerated."

A search of the dilapidated property in Salzburg, Austria, last month initially turned up 60 items. But a second search revealed a further 178 paintings, drawings and objects that have since been taken to a safe location for experts to restore and catalog, said Holzinger.

Once that has happened the collector plans to publish a list so potential claimants can come forward, he said.

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The trove of seized artworks even included unknown paintings by artists such as Henri Matisse, Marc Chagall and these two works by German artist Otto Dix. (Michael Dalder/Reuters)

Unlike most of the works found in Munich, the items discovered in Austria haven't been impounded by authorities.

Still, Gurlitt has instructed his lawyer to return all works that are "justifiably suspected of being Nazi-looted art." The 81-year-old, who has a court-appointed attorney, is in ill health and has come under pressure from the German government to give up any works stolen from Jews by the Nazis.

Matisse work is first set for return

A first such handover could take place soon, according to his representatives. The painting Femme assise (Seated Woman) by Henri Matisse will be returned to the heirs of deceased Paris-based art collector Paul Rosenberg, said Holzinger. One of those heirs is French journalist Anne Sinclair, the ex-wife of former International Monetary Fund chief Dominique Strauss-Kahn.

Gurlitt's lawyer Christoph Edel is currently in talks with six claimants over the return of other works, said Holzinger. Only about 3-4 percent of the collection — built up by his father Hildebrand Gurlitt, an art dealer who traded with the Nazis — is expected to be classified as looted art, Holzinger said.

The announcement came as further works of art were discovered hidden at a house belonging to Gurlitt in Salzburg — a trove that Austrian television said included a long-lost painting by Claude Monet.

"We are about to return a work from the Schwabing portion of the collection that is justifiably suspected of being looted art," Christoph Edel, a court-appointed lawyer for the 81-year-old collector, said in a statement.

"Discussions with other claimants have been constructive as well, and we expect to be returning additional works in the coming weeks."