Among those arrested Friday were three men and one woman of Spanish origin, and one man from Colombia. One of the Spanish men is the alleged leader of the operation, the ministry said.
Ministry officials said they believe the Colombian defendant to be the liaison for the drug ring, which allegedly shipped cocaine from South America to Spain.
The arrests took place in an industrial warehouse in Vall d'Alba, a city in the eastern province of Castellon, where police found 512 kilograms (1,130 pounds) of cocaine and several vehicles. Officials later uncovered a laboratory beneath a construction site where cocaine was supposedly processed.
Three more people allegedly involved in maintaining the drug laboratory have also been arrested.
Police also found a total of 250 million euros ($340 million) in cash in the house of one of the defendants.