Spanish police said they have shut down an alleged forgery ring selling fake Banksy artworks across the US and Europe for up to 1,500 euros ($1,642) a piece.

Investigators seized nine artworks during a raid of an apartment in the city of Zaragoza, northern Spain, according to Catalan police. A group operating from the property has been linked to some 25 sales — made through online platforms, auction rooms and antique shops — involving works attributed to Banksy, police said in a statement on Thursday.

The seized works were created on cardboard with spray paint using stencils, while ink seals and stickers were added to make them appear authentic.

Police said they have charged four people with fraud and intellectual property offenses. Two of the alleged fraudsters are suffering from “financial problems” and made copies of Banksy’s work before selling them at “reasonable prices no higher than 80 euros ($87),” the police statement said. The “main suspect” meanwhile had knowledge of the art world and is accused of passing the works off as genuine using forged certificates.

Investigators said Banksy’s Pest Control organization, the only body able to officially authenticate the artist’s work, has confirmed that pieces linked to the Zaragoza workshop are fake, as are the accompanying certificates. Police became suspicious after noticing that many similar works had become available on the market, the statement added.

Banksy started out as a graffiti artist in the British city of Bristol in the 1990s and has since become one of the art world’s most sought-after names thanks to his subversive statements and dark humor. His 2015 “Dismaland” installation — located in a British seaside town — was a twisted spin on Disneyland billed as a “bemusement park,” and featured a decrepit fairytale castle, a game where visitors navigated packed migrant boats through murky water and a high-interest loan store for kids seeking advances on their allowances.

Though the market value of his work has soared in recent years (his famous self-shredding work “Love is in the Bin” sold for a record $25.4 million at a Sotheby’s auction in 2021), Banksy continues to produce works in public spaces that make their preservation near impossible — and even invite theft or defacement.

The investigation remains open, and police said they are not ruling out more victims and further arrests.