The former Torrance State Hospital building in Derry Township closed in the late 1960s.
But in a news release Monday, police say trespassing continues to be a problem "due to people believing it is haunted."
Several Web sites and YouTube videos chronicle people's efforts to get inside the hospital to look for spirits.
Police announced the no trespassing edict saying the building's new owner doesn't want anybody on the property. On Aug. 15, police cited an 18-year-old Johnstown woman for criminal trespass.