Authorities have arrested at least 66 people in a European food scam which sold horse meat unfit for human consumption.

European Union police coordinating organization Europol announced Sunday that eight nations cooperated in the operation. In Spain, 65 people face a series of charges relating to public health, money laundering and animal abuse.

The operation took several months and the chief suspect, a Dutch businessman, was arrested in Belgium in April.

Spain's Civil Guard said that the criminal ring acquired horses in Spain and Portugal that were "in poor shape, old, or had been designated 'not apt for consumption.'" After falsifying paperwork and substituting microchips used to identify the horses, the animals were slaughtered and the meat shipped to Belgium.

Get Breaking News Delivered to Your Inbox

The Civil Guard said that the profits from the illegal meat could reach 20 million euros ($23 million) a year.

The case was linked to a 2013 scandal when Irish authorities detected beef burgers containing horse meat. At the time, horse meat was also detected in IKEA's popular Swedish meatballs.

Authorities in Belgium, France, Italy, Portugal, Romania, Switzerland, Britain and Spain cooperated in the operation.