While authorities have alleged that the suspects likely had links to an Islamic terror network, Spanish Prime Minister Jose Luis Rodriguez Zapatero attempted to downplay any planned terror attacks, the BBC reported Saturday.
"Let's be as cautious as is advisable in these cases, with regard to the scope, intentions and what this potential group of radical Islamist activists represented," Zapatero said.
The raids were conducted by a joint task force made up of National Intelligence Center officials and members of Spain's Civil Guard.
Authorities alleged that explosive materials were among the items seized during the raids, leading some to suggest the suspects may have been planning bombing attacks.
Islamist militants bombed the train system in the Spanish capital of Madrid in 2004 killing 191 people.