Düsseldorf based art adviser Helge Achenbach has been arrested on suspicion of fraud, Germany’s Bild reported on Wednesday. The 62-year-old adviser was arrested on June 10th, following his return from Brazil where he had been installing a project, Campo Bahia, in the German World Cup team’s clubhouse.

According to the paper, Achenbach has been accused of fraud by a family of Essen-based billionaires. According to a state prosecutor that spoke to Bild, the family alleges that Achenbach did not stay within the agreed upon conditions regarding the purchase of artworks and added unqualified markups in the works’ prices. Bild claims that an heir of the Albrecht family, who owns German supermarket giant Aldi (of which Trader Joe’s is a subsidiary), is the accuser.

Achenbach is currently held under what is called Untersuchungs-Haft, a pretrial investigatory detention phase typically enforced when authorities consider an accused individual a flight risk or fear that the individual might manage to cover up alleged crimes before an investigation is complete.

According to a subsequent report by the DPA, Achenbach’s family confirmed that he had been arrested, but members fervently denied the allegations against him. The news agency further claims that Bertold Albrecht’s widow is behind the allegations, with Achenbach’s family suggesting that the charges are personally motivated.

Achenbach, who was friends with Mr. Albrecht before his death in 2012, is among Germany’s most influential art advisers. He was a prominent figure on the Düsseldorf art scene, selling early works by Gerhard Richter and Andy Warhol beginning the 1970s and was a close friend of Jörg Immendorff. In 2010, the artist’s widow demanded €510,000 from the sale price of one of her late husband’s sculptures, a fee she claimed had been reached in an oral agreement.