A Portland school bus driver found ammunition in a backpack left on his bus Wednesday morning, school officials said.

After dropping students off at Roseway Heights School, the driver conducted his daily sweep of the bus and found a backpack with 22-caliber rounds inside, said Matt Shelby, spokesman for the Portland Public School District.

The driver returned to the school and alerted the principal.

Eventually, the student who owns the backpack was identified. The eighth grader said he found the ammunition while playing at his grandmother’s house. He told officials he collects ammunition and brought it home but forgot to remove it from his backpack.

School officials said they confirmed there was no malicious intent involved.

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The student, whose name was not released, was suspended.