What happened to a group of works by Anselm Kiefer, Renate Graf, and Markus Lüpertz that’s said to be worth €300 million (about $331.9 million)? According to a new report, the pieces have disappeared somewhere in China.

On Monday, Lüpertz held a press conference in Beijing to lament his vanished paintings—152 of them, to be exact, in addition to 87 paintings by Kiefer and 103 works by Graf. According to Süddeutsche Zeitung, the artist feared for his works’ well-being. “I used a special glue color in my early paintings” that is very sensitive to water, he said. If the paintings were now stored in a damp location, he continued, they could be ruined.

Maria Chen-Tu, a Taiwanese-born art collector with a German passport, is reportedly the person at the center of the art’s disappearance. According to Süddeutsche Zeitung, the works were acquired for her private holdings, the Map Collection; exhibitions of the collection were organized through Bell Art, the company of her partner since 2016, Chinese businessman Ma Yue.

“This is unique to the art market,” Wenzel Jacob, curator and former artistic director of the Bundeskunsthalle in Bonn, who worked with both, told the German outlet. “I have not encountered such a criminal case in my career.”

According to the report, the works’ disappearance is part of a larger pattern. Chinese painter Zhang Xi told Süddeutsche Zeitung that she had lent 27 paintings to Bell Art for exhibitions in Germany and never saw the works again or received any money for them. Ma Yue claims that his company never received the paintings. Meanwhile, German artist Uwe Esser also lent four of his artworks to Ma for an exhibition in Nanjing in 2015. The works were never reportedly returned, though Esser told the German paper that Ma’s employees offered him payment in cash, to be collected in person at Dusseldorf Airport without an invoice. Esser filed a complaint in response, and Ma will stand trial for embezzlement on January 24, 2020, in Krefeld, Germany.

Chen-Tu said in the Süddeutsche Zeitung report that the blame should rest with Ma, whose company has since been liquidated. Ma has denied all the allegations against him. The works, Ma claims, are accessible in Shanghai, Shenzhen, and Hong Kong, but he did not provide the German publication with exact details about their location.