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.

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.

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.

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.