Almost every aspect of the casino operator’s business was affected by the initial shutdown. Apparently, the outage affected reservation systems, booking systems, hotel key card systems, and casino floors.

In response to the cybersecurity issue, the company’s email systems were also taken down, and have not yet been restored.

Casino floors were back online as of Monday evening, according to the company. However, their reservation systems for their thousands of hotel rooms and restaurant reservations are still down more than a day after first reports of the incident surfaced.

There are thousands of hotel rooms operated by MGM in Las Vegas and across the country. According to SEC filings, their hotel operations generate more revenue than their casino operations. For the quarter ended June 30, Las Vegas rooms revenue was $706.7 million, while casino revenue was $492.2 million.

“We quickly launched an investigation with help from leading external cybersecurity experts,” MGM wrote on X, formerly Twitter. In addition, we notified law enforcement and took prompt action to protect our systems and data.