A subsidiary of Kyushu Electric Power (TYO:9508) has reported that an external backup storage medium went missing from an unlocked cabinet inside a secured server room.

The device contains customer names, addresses, electricity usage data, and phone numbers, but no bank account or credit card information, according to a Tokyo bourse filing on Tuesday.

The backup was created due to insufficient server capacity, and the loss was discovered on May 26 after being confirmed present on April 27.

No data leakage has been confirmed so far, and investigations have not ruled out unauthorized removal.

Authorities including the Personal Information Protection Commission have been notified, and affected customers will be contacted individually.

The company is continuing its search and will implement measures to prevent a recurrence.