PITTSBURGH (CBS) — Protesters violently smashed the windows of a Pittsburgh-area jail and damaged several police cars parked outside.

It happened at the Allegheny County Jail around 8 p.m. Monday.

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Pittsburgh Police say a group of 20 to 25 masked-people gathered outside of the facility.

They allegedly threw rocks, sticks and fired fireworks into the jail and nearby patrol cars.

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Police arrested 11 people.

Protesters say they were rallying for the rights of inmates.

None of the jail’s inmates or employees were hurt.

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The protesters reportedly ran off once they were confronted by a police officer.