MGM Resorts has suffered a “cybersecurity” incident, leading to the shutdown of certain hotel and casino systems at properties in the United States.

According to reports, the event took place on Sunday, however the company is still evaluating the total extent of the breach which could have affected systems across numerous properties within the US.

According to the Associated Press, the US Federal Bureau of Investigation (FBI) is “aware of the incident”, which it classified as “ongoing”.

MGM has since noted that it found a “cybersecurity issue affecting some of the company’s systems” and has tapped external experts, while noting that its mitigation efforts involved “shutting down certain systems”.

As of Tuesday morning, MGM Resorts’ website was ‘currently unavailable’, with customers being directed to make reservations by phone.

MGM China, as of Tuesday morning, had yet to issue a statement notifying whether any of its services had been affected by the breach, however its website and booking services were still accessible.

Cyberattacks have become more strategic within recent years, as hackers increasingly aim to access major corporations via third parties.