ST. PAUL, Minn. (WCCO) — A St. Paul community school was evacuated Friday morning after a hollowed-out grenade was found in a student’s backpack, according to district officials.

Police were called to Heights Community School on the city’s east side just after 11 a.m.

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Heights is part of the St. Paul Public School district, and serves students from prekindergarten through fifth grade.

The district enacted emergency procedures and evacuated all 550 students from the building and into buses outside.

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Police say the grenade was hollowed out and was not a threat, and the student who brought it also knew it was safe.

District policy, however, still considers it a weapon, and the student could face expulsion.

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Students returned to the building within 30 minutes of the evacuation.