Updated 03/05/15 – 1:11 p.m.

CHICAGO (CBS) — A Hoffman Estates hospital was placed on lockdown, and employees were later evacuated, while police investigated what turned out to be a false alarm for an active shooter in the building.

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Hoffman Estates Police Lt. Darin Felgenhauer said police received a call at 9:20 a.m. about an automated active shooter alarm at Alexian Brothers Behavioral Health Hospital at 1650 Moon Lake Blvd.

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Police quickly determined the alarm likely was activated by accident. A search of the building turned up no gunman and no firearm, according to Felgenhauer.

Hospital representatives a construction crew working on a project in the building accidentally set off the alarm.

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Several people were seen evacuating the building with their hands in the air as police were on the scene, but the hospital said they were given the all-clear at 11 a.m.