The Man Ray Trust, the organization overseeing the Surrealist artist’s estate, has claimed that a Christie’s sale of Surrealist art from the collection of the artist’s former assistant contains stolen work.

The sale, which takes place today in Paris, comprises 188 works, including Man Ray’s portraits of socialites, muses, and artists, as well as readymades by his friend Marcel Duchamp. The group of works once belonged to Lucien Treillard, Man Ray’s former assistant, who died in 2003, and was consigned by the assistant’s widow, Edmonde Treillard. The sale is expected to fetch €1.8 million–€2.6 million ($2.2 million–$3.1 million).

“Contemporaries of Man Ray and Juliet Man Ray advised the Man Ray Trust that there is significant reason to believe Lucien Treillard stole a substantial number of Man Ray’s works and possessions immediately following his death,” the Man Ray Trust said in a statement. The organized claimed that, of the 188 works being auction, 148 should not head to sale. It also alleged that Christie’s did not seek copyright permissions for images of the works it is selling.

Steven Manford, an art historian enlisted by the Trust to review the sale, said that the cataloguing and essays done as part of the sale “fall far short” of Christie’s standards.

Although the Trust demanded that the sale be canceled, Christie’s said it plans to move forward with the auction. “We would not offer any work for sale if we had any reason to think that there are any issues with the works or that ownership could not pass freely to our buyers at auction,” a representative for Christie’s said. “We have given very careful consideration to the concerns raised by the Man Ray Trust.”

The dispute is the latest episode in a long-running saga involving the artist’s estate. In the past, there has speculation about the authenticity of certain Man Ray works. Much of this scrutiny has revolved around Lucien Treillard, a history teacher who served as a part-time assistant to Man Ray for around a decade, until the artist’s death in 1976. After that, Treillard went on to produce unauthorized replicas of Man Ray works as commercial demand increased.

The Man Ray Trust has claimed that Treillard took advantage of access to Man Ray’s studio after his death. Treillard has admitted in the past to having falsely authenticated Man Ray work.

When it comes to the current sale, Richard Hamlin, a Man Ray Trust board member, who is married to Stephanie Browner, an heir to the Man Ray estate, claimed that the works coming to auction should belong to the heirs of Juliet Man Ray, the artist’s late wife. “We had no idea [about] the extent of this theft,” he told ARTnews, explaining that record-keeping around the posthumous estate was not always as detailed as it could have been.

While the Trust has long been aware of Treillard’s practice of continuing to reproduce material he acquired from Man Ray’s studio under unclear circumstances, it has never pursued legal recourse against the former assistant, claiming that it lacks the legal resources to do so. For years, the original trustees of the estate believed the works would be gifted to the Centre Pompidou in Paris, where a vast archive of Man Rays work resides.

According to Hamlin, representatives of the Man Ray Trust and its legal counsel approached Christie’s and asked the house to submit deeds of sale and various forms that would authenticate the works coming to auction. Hamlin alleged that Christie’s did not supply such documents. (A Christie’s representative confirmed that the house’s counsel consulted with the Trust’s attorney, but declined to comment on the specifics, citing a confidentiality agreement.) In its release announcing the sale, Christie’s claimed that a committee devoted to Man Ray’s art authenticated the works.

In the past, speculation around the mishandling of Man Ray’s posthumous estate has impacted the artist’s market. In 1998, the sale of Man Ray’s Noire et Blanche (1926) sparked a dispute over its provenance record, when it sold for a then milestone price of $607,500 at Christie’s. Resulting questions arose over the authenticity of select Man Ray photographs.

Many of the works in the Christie’s sale were held by Treillard for decades, and some where purchased through dealers. The leading lot is a 1963 Duchamp Boîte-en-Valise work containing 68 reproductions of the Dadaist’s works. It estimated at €200,000–€300,000. Man Ray readymades are included in the sale, including Object to be destroyed – Perpetual Motif (1971), a metronome whose pendulum features a photograph of Lee Miller’s eye, which is estimated at €25,000–€35,000 ($30,000–$42,000).

Christie’s auction is the largest sale devoted to the artist since 2014, when Sotheby’s sold around 400 lots from the Man Ray Trust for $3.7 million. Prior to that, in 1995, following a settlement with the French state, the Juliet Man Ray estate sold 500 lots from Man Ray’s archive at Sotheby’s for $6 million.

Hamlin said that the Trust felt compelled to call for the cancelation of the auction because of the breadth of the works headed to sale and the intimate nature of many of them. “You’re talking about a treasure trove and things that were very personal,” he said, adding, “If we think that there is trust property that someone is disposing of improperly, then we have the duty to act.”