In a message to its customers, Sony said: "We had previously believed that SOE customer data had not been obtained in the cyber-attacks on the company."
However, it added that "on 1 May we concluded that SOE account information may have been stolen".
Sony was quoted by the Associated Press (AP) news agency as saying that the latest incident occurred on 16 and 17 April.
This was earlier than the larger Playstation user security breach.
Apparently it adds another 25m accounts to the haul.