FORT WASHINGTON, Pa. (CBS) — A prank led to the lockdown of a high school in Montgomery County Friday morning, a school official said.

Upper Dublin High School on Loch Alsh Avenue was placed on lockdown shortly after 9 a.m.

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According to Michael Pladus, the superintendent of the Upper Dublin School District, a lockdown was ordered at the school after some type of graffiti was found in one of the female bathrooms.

Police were called to the school and it was later determined that the graffiti was a prank.

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The lockdown was lifted at about 9:30 a.m. and students were back in their classrooms.

The incident remains under investigation.

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