Three teenagers including a 15-year-old boy are being investigated on suspicion of being part of an international £1 million card fraud gang.
West Midlands Police said the region's organised crime unit swooped on homes in Great Barr, Birmingham, and the Cheylesmore area of Coventry on Tuesday as simultaneous raids were carried out in Finland, Spain and Canada.
An 18-year-old man was arrested from the Birmingham address on suspicion of fraud and cybercrime offences and has since been bailed by police until next year.
Officers said a 15-year-old male was also spoken to by officers during the inquiries, while a 16-year-old male was identified from the Coventry address as potentially being involved in the fraud.
Detective Inspector Rob Harris said: "This is a wide-reaching investigation - one that was launched back in January this year - involving Europol, authorities on the continent, and the Royal Canadian Mounted Police.
"We've played our part by executing warrants at addresses in the West Midlands suspected of being linked to the card scam investigation and cybercrime offences that's seen websites compromised and accounts taken over.
"Computer equipment and other digital devices have been seized from the properties and these will be forensically examined."
The investigation aims to dismantle an organised crime group believed to have harvested details from more than 6,000 credit cards which have been used to attack some 170 e-merchants.
It is believed the stolen card details have been used to carry out transactions before being sold on to other crime networks.