MADRID , Spain ( CNN ) -- Police arrested 13 men in Barcelona and Valencia early Tuesday on suspicion of working in an international document forgery ring , possibly with links to Islamic terrorists , a police statement said . Spanish police detain a suspect following the arrests in Valencia and Barcelona Tuesday . `` There are arrests . The police have to determine who is who , '' a government source told CNN . The suspects include 11 Pakistani nationals , an Indian and a Nigerian . Most of the arrests were in Barcelona , Spain 's second-largest city , but two were in Valencia , the third-largest city , also on the Mediterranean coast , south of Barcelona , the police statement said . The ring , in addition to providing forged passports , also trafficked in drugs and human beings , in a network stretching to Britain , France , Germany , Belgium , Switzerland and Thailand , and police in those countries were part of the investigation , the statement said . The ring operated by stealing passports in various Spanish cities and sending them to Thailand , where they were altered and sent to the other five European countries to criminal networks , to facilitate fraudulent border crossings . Investigators in all of the countries involved were now searching for links between the passport forgery ring and Islamic terrorists , the statement said . Police searches of locales in Barcelona and Valencia turned up material to forge documents , dozens of passports , some already forged and others blank and waiting to be filled in , passport-sized photographs of numerous people , computer information and cell phones . Police did not mention finding any weapons or explosives in their searches . The operation was coordinated by a judge at Spain 's anti-terrorism National Court in Madrid .
Most of the arrests were in Barcelona , according to Spanish media . Police seize blank passports , national identity cards , Spanish media report . Police look for a printing machine in Valencia , one source says . Others : Police say ring also found in Italy , France , Germany , Belgium among others .