CNN  — 

US investigators seized artworks by Austrian painter Egon Schiele from three museums amid claims Nazis stole them from a Jewish collector during World War II.

Museums in Chicago, Pittsburgh and Oberlin, Ohio were named in search warrants issued by New York state’s Supreme Court, which said it has “reasonable cause” to believe that the works in their collections are “stolen property.”

The Manhattan District Attorney’s office declined CNN’s request for comment on the nature of its investigation, though all three artworks — the Chicago Institute of Art’s “Russian Prisoner of War,” Carnegie Museums of Pittsburgh’s “Portrait of a Man” and the Allen Memorial Art Museum’s “Girl with Black Hair” — are currently part of civil lawsuits filed by the heirs of Fritz Grünbaum.

Prior to the war, Grünbaum, a well-known Austrian comic, cabaret star and songwriter, amassed an art collection of almost 450 works, according to court documents filed by his heirs. Among them were 81 artworks by Schiele, an expressionist painter and protégé of Gustav Klimt.

Egon Schiele's "Girl with Black Hair" is among the works that the heirs of Jewish collector Fritz Grünbaum say were stolen by the Nazis during World War II.

In 1938, Grünbaum was sent to Dachau concentration camp, where his heirs say he was tortured and “compelled … to sign an unlawful power of attorney” over to his wife before he was murdered in 1941. Court documents claim that his wife, Elisabeth, was then “forced to liquidate” his assets, including his art collection, which was looted and dispersed by the Nazis. She, too, was later killed in a concentration camp.

The three seized items, which include watercolor and pencil works on paper, were produced during the later years of Schiele’s life, between 1911 and 1917. Investigators have valued each at between $1 million and $1.5 million.

A spokesperson for the Art Institute of Chicago said the museum is “confident” in its “legal acquisition and lawful possession of this work,” adding the matter is “being properly litigated” in the ongoing civil suit.

Oberlin College also expressed confidence that its Schiele watercolor had been “legally acquired” and was “lawfully possess(ed)”, adding: “We believe that Oberlin is not the target of the Manhattan DA’s criminal investigation into this matter.”

Egon Schiele's "Portrait of a Man," one of three artworks by the Austrian painter seized by US investigators amid claims that the Nazis stole them from a Jewish collector during World War II.

A Carnegie Museums of Pittsburgh spokesperson meanwhile told CNN that the institution is “deeply committed” to its “mission of preserving the resources of art and science by acting in accordance with ethical, legal and professional requirements and norms.”

“We will of course cooperate fully with inquiries from the relevant authorities,” the statement added.

The search warrants specify that the three items be seized “in place,” meaning they may, for now, remain at the museums.