Six artworks stolen by the Nazis and returned recently to the heirs of the Austrian Jew who owned them will be auctioned in New York next month, Christie's said Thursday.

New York authorities announced on September 20 that leading institutions that include New York's Museum of Modern Art had agreed to return seven works by the Austrian Expressionist artist Egon Schiele to the family of Fritz Grunbaum, a cabaret performer and art collector who died in the Dachau concentration camp in 1941.

Three of the works -- watercolors on paper, thought to be worth up to $2.5 million each -- will be auctioned on November 9 and three others will go up two days later as part of Christie's fall auctions.

The seventh work, which was returned by the Museum of Modern Art, has been acquired privately by "a prominent collector who has a demonstrated record of supporting Holocaust survivors," said Raymond Dowd, the Grunbaum heirs' New York attorney.

Grunbaum's heirs had been fighting for the artworks' return for years. He owned hundreds of works of art, including more than 80 by Schiele.

Schiele's works, considered "degenerate" by the Nazis, were largely auctioned or sold abroad to finance the Nazi Party, according to the Manhattan district attorney's office.

Arrested by the Nazis in 1938, Grunbaum was forced while at Dachau to sign over his power of attorney to his spouse, who was then made to hand over the family's entire collection before herself being deported to a different concentration camp, in current-day Belarus. 

The seven works whose restitution was announced last month had reappeared on the art market after World War II, first in Switzerland and then making their way to New York. 

The Grunbaum heirs are pursuing other works as well. 

Last week, three Schiele drawings were seized by the Manhattan district attorney's office from the Art Institute of Chicago, the Carnegie Museums of Pittsburgh and the Allen Memorial Art Museum at Oberlin College in Ohio.

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