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. 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. The Press of Atlantic City reports MGM owns Borgata Hotel Casino & Spa in Atlantic City. As of 3 p.m., a message on the casino’s website said the site was unavailable and left a phone number to call for assistance.