Police near Athens raided the first of its kind cocaine lab and arrested five suspects, including a Briton.
The Finance Ministry, whose fraud department handles such operations in Greece, said information for the operation leading to the raid was provided by the U.S. Drug Enforcement Administration and Greece's National Intelligence Service.
The ministry's fraud agency said a British man, two Venezuelans and two Albanians were arrested on drug trafficking charges. Authorities did not release their identities.
Agency officers seized 26 kilograms (57 pounds) of cocaine and drug manufacturing equipment at the lab, located on the coast about 50 kilometers (30 miles) south of Athens, agency spokesman Giorgos Papadopoulos said.
The agency said the suspects were believed to be linked to a Colombian drug cartel.
An agency statement said the lab used "primary materials" to manufacture cocaine. It said it was the first time such a lab had been found in the EU, but did not give other details.
Greece has pledged to expand cooperation with overseas agencies to fight trafficking.
Earlier this month, Greek police arrested one of Australia's most wanted men, convicted cocaine trafficker Tony Mokbel.
He is facing extradition to Australia to serve a sentence of at least nine years and face additional charges for drug trafficking and murder.