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HAVERTOWN, Pa. (CBS) — Haverford High School was evacuated on Wednesday after threatening graffiti was found on a school wall that referred to an explosive device.

The Haverford School District said “out of an over-abundance of caution,” the students were dismissed and the building was evacuated.

Police are investigating the incident.

The school district says that once police clear the area and decide that the building is safe, evening activities will resume as scheduled at the high school.

No one was injured in the incident.

Stay with CBSPhilly.com for this developing story.