COLUMBUS, Ohio — State authorities are investigating a string of threats made against schools across Ohio.
Threats have caused evacuations or closures of some schools in the past week, although there haven't been police reports of finding explosives.
The state Department of Education says it doesn't know how many schools have been threatened, but says Ohio Homeland Security has reported "a number of bomb threats."
Education spokeswoman Kim Norris says schools are urged to work closely with law enforcement, taking all threats seriously. They also ask students and parents to be alert and to report anything unusual.
In southwest Ohio, Butler County Sheriff Richard Jones reported Wednesday that two school districts in his county received unsubstantiated threats, with more in neighboring counties. Some schools described calls with voices sounding computer-generated or automated.