STOCKHOLM, July 5 (Reuters) - Sweden"s financial watchdog said on Monday it was investigating payments firm Klarna over a potential breach of banking secrecy laws in connection with an IT incident at the firm in May. For a 30 minute period on May 27, Klarna customers were shown other users" data - a digital mishap which the firm, in a statement on June 4, blamed on human error. "(We) will investigate whether Klarna has violated bank secrecy in connection with an IT incident in May where the bank"s customers were able to access information about each other for a limited time," Sweden"s Finansinspektionen said in a statement. A spokesperson for Klarna told Reuters that the probe, "was very much expected as part of our regular dialogue with the Swedish FSA and as always we approach this with full cooperation and transparency." Customers card details were not part of the information accidentally shown to other users, Klarna said in June. The watchdog said the issue around bank secrecy would be added to a more general survey it announced in March into Klarna"s processes for handling information and cyber security risks.