'MGM Resorts recently identified a cybersecurity issue affecting some of the company's systems,' the company said in a statement that pointed to an investigation involving external cybersecurity experts and notifications to law enforcement agencies. The incident began Sunday and the extent of its effect on reservation systems and casino floors in Las Vegas and states including Maryland, Massachusetts, Michigan, Mississippi, New Jersey, New York and Ohio was not immediately known, company spokesman Brian Ahern said. LAS VEGAS - A 'cybersecurity issue' led to the shutdown of some casino and hotel computer systems at MGM Resorts International properties across the U.S., a company official reported Monday.