LONDON -- Unknown works by artists such as Marc Chagall and Henri Matisse, works thought lost to the ravages of war and others deemed "degenerate" or looted by the Nazis form part of the spectacular trove of art discovered by German authorities in the apartment of an elderly recluse in Munich.
Two days after news of the find broke, southern Germany officials revealed Tuesday that the hoard contains 1,406 pieces by masters whose names are a who's who of Western art of the last 150 years: Pablo Picasso, Pierre-Auguste Renoir, Henri Toulouse-Lautrec, Gustave Courbet, Oskar Kokoschka, Emil Nolde.
But the collection goes back further, with items by 16th-century artist Albrecht Durer and 18th-century painter Canaletto -- works that have not been publicly seen for decades, if not longer.
"When you stand in front of works and see these long-lost works in good condition that were thought to have been destroyed, that is such a happy feeling," said Meike Hoffmann, an art expert at the Free University of Berlin, who has been examining the haul. "The pictures are of extraordinary quality and are of huge scientific value. Many works were not known before."
Among the new discoveries are an allegorical scene by Chagall, a rare self-portrait by Otto Dix and an untitled painting of a woman attributed to Matisse that probably dates to the 1920s.
Authorities seized 121 framed and 1,285 unframed works from the Munich apartment of Cornelius Gurlitt, son of a well-known Nazi-era art dealer, in a raid in early 2012. These include oil paintings, watercolors, etchings and drawings.
Reinhard Nemetz, a state prosecutor in the city of Augsburg, near Munich, said there was "concrete evidence" that some works had been plundered or confiscated by the Nazis during their persecution of Jews or campaign against what leader Adolf Hitler denounced as "degenerate art."
Yet determining whether Mr. Gurlitt himself is guilty of a crime is a complex matter. The 80-year-old is under investigation for possible tax evasion and embezzlement, but Mr. Nemetz acknowledged that police are not in touch with him and have not arrested him, despite having impounded the astonishing contents of his flat. "We currently have no contact with the suspect," Mr. Nemetz told reporters. "But there is no urgent suspicion that would justify a warrant."
The raid on Mr. Gurlitt's home, the culmination of a long investigation, occurred over a three-day period, from Feb. 28 to March 2, 2012. That is a year later than was originally reported by the German magazine Focus, which broke the story of the remarkable discovery this past weekend.
Since word of the cache emerged, advocates of returning art looted during the war have criticized German officials for keeping quiet so long, and for failing to issue an inventory as quickly as possible, to allow heirs of the original owners to reclaim what was stolen.
Mr. Nemetz said keeping the works safe was crucial, and that their security could have been compromised by a media frenzy surrounding news of their discovery. He does not intend to exhibit or publish images of the entire stash, and it will be up to people who believe that a former family possession might be included to contact his office.
The report in Focus magazine estimated that the works could be worth more than $1.3 billion, but Mr. Nemetz said his office had not made any determination of the cache's monetary value.
Preliminary research is underway on 500 of the 1,400 items so far, Ms. Hoffmann said. Documenting and authenticating the pieces could take years, especially those not in catalogs or on lists of the artists' known works.
Tracing transfers of ownership, through both private and public transactions (such as at auctions and through museums), can be difficult because many records from the wartime era have not survived, including those kept by the Nazis.