FLAGSTAFF, Ariz. (AP) — Flagstaff schools have received a series of threatening notes.

The Arizona Daily Sun reported that Flagstaff police are investigating a note found Thursday in the girls’ bathroom at Flagstaff High School. A second note was found on the wall in a girls’ bathroom at Thomas Elementary School.

This week’s notes are the latest in a series that have been found at Flagstaff schools. A student found a note in a boys’ bathroom at Flagstaff High School on March 8 warning there would be a shooting at school. On March 9, a note about a school shooting was found in the girls’ bathroom at the high school. A third note was found Monday.

The most recent note at the school referenced the previous notes.

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