(CBS) – Senior Prank Day took a chaotic turn Thursday at Morton East High School after someone tossed a lit smoke bomb into a classroom.

The explanation from Cicero spokesperson Ray Hanania comes after police responded to a disturbance at the Austin Boulevard school around 3 p.m.

A student apparently lit and tossed a non-explosive smoke bomb into a classroom. The stunt coincided with “Senior Prank Day” – the last day seniors were present in school — and authorities were expecting something might happen, Hanania said.

No one was injured. The fire department was called as a precaution, and the school was emptied of students.

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