OLNEY, Md. — Police in Maryland have charged four 13-year-old boys they say were involved in clown-themed social media threats against middle school students.

Montgomery County police announced Thursday that they charged the boys as juveniles with making threats of mass violence. Police nationwide have been dealing with similar hoaxes involving threats or reports of violence by people dressed as clowns.

Police were notified Monday of threats made against several students at Rosa Parks Middle School in Olney from a clown-themed Instagram account. Police say investigators used details from the posts and information from victims, their parents and school administrators to identify the suspects. The boys were arrested and charged Wednesday, then returned to their parents’ custody.

The case has been referred to the Department of Juvenile Services.