This combo of images provided by the Manhattan District Attorney’s Office,

Manhattan District Attorney’s Office via AP

The seven Schiele works were “Portrait of the Artist’s Wife, Edith,” “Girl Putting on Shoe,” “Standing Woman,” “Seated Woman,” “Self Portrait, “I Love Anthesis” and “Portrait of a Boy.” The works range in value from $780,000 to $2.75 million.

Grünbaum’s heirs have allegedly sought the return of the works for decades through the courts.

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He added, “We still have so much to learn from Fritz Grünbaum and these seven pieces that he found to be so beautiful. The Manhattan District Attorney’s Office is proud to have played a role in remembering his legacy.”

In response to the seizure of the Schiele artwork, a spokesperson for the Art Institute of Chicago tells PEOPLE, “We are confident in our legal acquisition and lawful possession of this work. The piece is the subject of civil litigation in federal court, where this dispute is being properly litigated and where we are also defending our legal ownership.”

The spokesperson also says that the Manhattan District Attorney’s Office has moved to seize the work “in place” and it remains in the museum’s custody at the moment.

In a statement to CNN, Oberlin College, which oversees the Allen Memorial Art Museum, said that its Schiele work was acquired legally. The institution added: “We believe that Oberlin is not the target of the Manhattan D.A.’s criminal investigation into this matter.” A spokesperson for the Carnegie Museums told the outlet: “We will of course cooperate fully with inquiries from the relevant authorities.”

The Manhattan District Attorney’s Office, the Carnegie Museums of Pittsburgh and the Allen Memorial Art Museum did not immediately respond to PEOPLE’s requests for comment.

source: people.com