A massive collection of 1,500 works of art, including Picassos and Matisses, have been found in a Munich basement, more than 70 years after they are believed to have been plundered during the Nazi period.
If the paintings are confimed by art authorities, it will be the largest ever recovery of stolen art, according to German magazine Focus, which broke the story.
About 200 of the works already had international warrants on them.
The works were reportedly confiscated or forcibly sold to the Nazis in the 1930s and 1940s, with many of the works likely considered "degenerate" by the fascist movement.
Investigators say the collection is worth about 1 billion euros, or $1.35 billion.
The younger Gurlitt was suspected of tax evasion. He had apparently held on to the works and sold them occasionally when he needed money.
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Hildebrandt Gurlitt, acting on orders from the Nazi party, had allegedly acquired the paintings and sketches for very little money from Jews during the Nazi period.
The tax investigation into his son was begun after he was stopped on a train in Switzerland with large sums of cash on him.
Most modern art was banned by the Nazis — labelled "degenerate," un-German or condemned for being created by Jewish artists.
Some works were destroyed while others were confiscated.
It is believed that about 16,000 works of art were confiscated by the Nazis.