GRAND FORKS, N.D. (AP) — Hundreds of employees at the Ralph Engelstad Arena in Grand Forks are affected by a data security breach.

The general manager of the arena, Jody Hodgson, sent a message to employees Tuesday that said the breach resulted in the access to some employee payroll files. About 320 employees are affected and will be getting a notification letter in the mail on steps to protect their personal data.

Hodgson says investigators, including the FBI agents, believe the suspect is an international entity specializing in cyberattacks and ransomware attacks. Arena executives say they have since taken additional steps to protect the venue’s data.