Several major hotels in Las Vegas, including the Bellagio, were left with faulty door locks, inoperable slot machines and other problems Monday after hotel officials said they were hit with a cyberattack.

The FBI said it is investigating the attack on MGM Resorts International hotels early in this morning. The company said "it took prompt action to protect our system and data, including shutting down certain systems."

"Our investigation is ongoing, and we are working diligently to determine the nature and scope of the matter," MGM said in a post on X, formerly known as Twitter.

The company would not provide additional details of what was affected, however, it appeared to disrupt several key hotel systems.

Bellagio guests were unable able to charge anything to their rooms, make reservations, or use their digital room keys, according to ABC affiliate KTNV.

Several slot machines also appeared to be out of service at the Aria casino, KTNV reported.

The MGM international website was also down, and not allowing for online bookings. The site redirected customers to their hotel's phone numbers for help.