Criticism over a late billionaire’s jewelry auction is growing louder, as activists claim the assets were purchased with money plundered from Jewish people in Nazi Germany. The jewels come from the collection of Heidi Horten, whose late husband, Helmut, was allegedly a “member of the Nazi party,” according to Agence France-Presse. Helmut Horten built a fortune in the textile industry, but he gained control over multiple businesses only after the former Jewish owners were forced to flee. In a statement on May 5, the American Jewish Committee said that the auction—which is projected to bring in $150 million or more—“should be put on hold until a serious effort is made to determine what portion of this wealth came from Nazi victims.” Christie’s, which is facilitating the auction, has said it will make a donation to Holocaust research and education causes.