Computer systems at both card makers were breached recently, allowing hackers to get away with data on thousands of banking cards, the Aftonbladet newspaper reports.

The hacking at Visa took place in Spain and the company won’t say exactly how many cardholders may have been affected.

Nevertheless, a number of Swedish banks have begun notifying customers about the incident.

“Where there is a risk that the cards may be misused, we contact customers and ask them to block their cards so that we can exchange them,” said SEB spokesperson Kerstin Ottosson to the TT news agency.

“For us, there are about 28,000 cards which have been affected, but I can’t say how many of them will need to be exchanged.”

Swedbank spokesperson Jenny Clevström said the bank was aware of the breach, but that no Swedbank customers were affected.

“But we’re going to exchange a few cards as a precautionary measure,” she told TT.

Helena Östman of Nordea said the bank had been notified by both MasterCard and Visa about the problem.

A customer with ICA Bank told Aftonbladet that he had been informed by the bank that his card had been blocked due to a breach at MasterCard somewhere in Europe.

Handlesbanken also took steps to notify affected customers on Tuesday.

“We’ve gone out with information today that a card manufacturer may have been hacked in another European country,” Handlesbanken spokesperson Bengt Carlsson told the newspaper.