Sony Corp.’s PlayStation Network and Qriocity online services remain shut as of today, Shigenori Yoshida, a Tokyo-based spokesman said. Sony is uncertain when it can resume the services, Yoshida said by phone today.

The company is in the process of adopting an improved security system and its plan to restart the services fully by May 31 is unchanged, he said. Sony shut down the PlayStation Network and Qriocity services April 20 because of possible data theft by hackers.

The maker of PS consoles had planned to restart partial operations within a week after boosting the level of security system, the company said May 1.