Spanish police have arrested more than 40 people suspected of laundering millions of euros to finance Colombian rebels from the FARC.
250 officers carried out nearly 30 raids, while similar operations took place in Colombia and Ecuador.
Police believe drug trafficking has enabled the launderers to stash away more than 200 million euros.
The raids follow a two-year investigation by police. In August 2008 they noticed a significant increase in money transfers from Spain to Latin America.
Colombian police identified where the money was going: to finance the FARC. They discovered that one of the beneficiaries of the transfers was wanted for murder and terrorism and had links with five known guerillas.
The source of the funds is thought to be cocaine production. Latin America is a major producer; Spain the main entry port into Europe.
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