The ringleaders of a forgery scam in Finland were sentenced to prison and ordered to pay €13 million ($11.4 million) in damages for selling hundreds of fake artworks over five years.

A district court in Helsinki determined that the married couple at the center of the allegations, gallery owners Kati Marjatta Karkkiainen and Reijo Pollari, duped private collectors and auction houses into paying millions of dollars for paintings purportedly by blue-chip modernists and Impressionists such as Henri Matisse, Pierre-Auguste Renoir, Claude Monet, and Wassily Kandinsky; lesser-known Russian romanticists; and works by the popular 19th-century Finnish painter Albert Edelfelt.

The two were each found guilty of 30 counts of aggravated fraud. Karkkiainen was sentenced to four years behind bars, while Pollari was handed a five-year sentence. Additionally, eight accomplices were also found guilty and given sentences of up to three years in prison.

For a long time, the couple’s scam went unnoticed. But the scheme started to unravel when a number of their fakes were identified on the market, prompting authorities to investigate the matter as a possible crime.

According to the press agency AFP, the most expensive forgery the couple managed to sell was a €2.2 million work purportedly by the French painter Fernand Léger. In its written judgement, the court adopted a surprisingly connoisseurial tone, stating, “The subject of the painting was in itself typical of Léger, considered a forerunner of pop art. However the treatment of the subject was incredibly weak and the painting style was childish.”

In total, investigators rounded up and handed over more than 220 suspect canvases to art historians and conservation experts at the Finnish National Gallery for analysis. After conducting a series of tests, they determined that the vast majority of them were fake. Investigators traced the counterfeit works to a self-taught artist based in southern Finland with a previous conviction for an unrelated case.

Most of the counterfeit works have now been seized by Finnish authorities. But investigators say that there may be more works by the scammers still circulating on the market.