DANVERS (CBS) – More than a dozen shell casings were found in a bathroom on the Essex Technical High School campus.

Thirteen empty casings were found in a boys’ restroom next to the concession stand at the school stadium.

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There were two girls’ lacrosse games at the stadium against North Reading and a track meet Wednesday.

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It’s unclear who left the casings and who found them, but they were reported to school personnel late Wednesday afternoon. Parents were quickly notified.

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Danvers Police were called to the scene and are investigating.