STORRS, Conn. (AP, Oct. 5, 2016) — Carrying golf clubs, shovels and hockey sticks, several hundred University of Connecticut students gathered just before midnight in a cemetery, ready to do battle with menacing clowns they had heard might be lurking among the headstones.

Police determined that Monday's clown rumors were a hoax. But dozens of similar reports have surfaced across the country, largely on social media. And authorities are being forced to take them seriously as a potential threat to public safety, particularly at schools, where principals have conducted lockdowns and canceled clas...