Spain’s Civil Guard has arrested three people in the cities of Zaragoza and Tarragona for trying to sell fake Joan Miró, Pablo Picasso, and Henri Matisse drawings, El País reports. They have been charged with crimes against intellectual property and fraud.

It is the culmination of Operación Mirones (Operation Voyeurs), launched in July 2014 to put an end to an art forgery ring. The investigation kicked off during a routine check at the border control in Lleida, when the Civil Guard stopped an Andorran resident carrying a series of Miró drawings and their certificates of authenticity. The agents, suspicious, asked experts to analyze the works, which were confirmed to be fake.

The suspect was promptly put under surveillance. And police soon observed that he was making regular trips to Zaragoza, where he would meet with dealers and collectors and try to peddle the forgeries as the real deal. It was also discovered that the suspect began storing the drawings in the office of a relative, a lawyer who works in Tarragona, in order to avoid further searches at the Andorran border control.

Aside from the the Andorran citizen, the Civil Guard arrested two other individuals, including a Zaragoza-based art dealer, who allegedly served as a middleman. According to ABC, the suspects were trying to sell the counterfeits for hundreds of thousands of euros.

During the operation, nine artworks were seized: six attributed to Miró, two to Matisse, and one to Picasso. The operation has also prevented the sale of two fake lithographs attributed to Miró.

The arrests come amid a spike in art forgery cases in Spain. In April 2014, Spanish art dealer Jose Carlos Bergantiños Diaz and his partner were arrested in connection to the infamous Knoedler & Co. art forgery scandal. They stand accused of selling more than $33 million worth of forgeries attributed to Mark Rothko, Jackson Pollock, and Robert Motherwell, among others.