The Plainfield Police Department reported that officers were called to Heritage Grove Middle School, 12425 S. Van Dyke Road, after a lockdown alarm was triggered around noon on Tuesday.

Plainfield police reported on Facebook, that officers “met with the staff and quickly determined it to be an accidental activation” after arriving at the school.

Despite being determined as a false alarm, police reportedly conducted a precautionary walk through of the entire building before releasing the lockdown and allowing staff and students to return to their regular school day.

In the statement, the Plainfield Police Department thanked the Heritage Grove staff “for their quick assessment of the situation.”

Police did not state in the report what caused the accidental alarm, or how staff determined it was a mistake.

The accidental alarm in Plainfield is the second Will County school to experience a falsely triggered lockdown alarm this week, following a similar incident which left Lockport Township High School’s East Campus on lockdown for several hours on Sept. 16.