Four 13-year-old boys have been charged for clown-themed social media threats against middle school students in Montgomery County, Maryland, police say.

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. Investigators used details from the posts and information from victims, their parents and school administrators to identify the suspects, police said. The boys were arrested and charged Wednesday, then returned to their parents' custody.

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

Two students were arrested for similar charges in Prince George's County earlier this week.