Colony Middle School in Palmer was closed down Thursday afternoon after a student made a "credible threat of harm," Principal Mary McMahon said in an email sent to parents.
Alaska State Troopers responded and removed the student, the email said.
"Further investigation (led) to the decision to close the school this afternoon until law enforcement and district personnel can sweep the building for any potentially dangerous object," McMahon wrote.
The school would be cleared Thursday evening and open for school Friday morning, she wrote.
"Your child's safety is my number one priority, and we are taking extreme measures to ensure there is no risk to students," McMahon wrote.
A spokesperson for the Matanuska-Susitna Borough School District did not immediately return requests for comment.
Troopers responded to a Palmer school at 12:34 p.m. after a report of a "written threat towards the school and students," the agency said in its daily online dispatches, but a spokesperson did not immediately confirm whether it was the same incident.
A 13-year-old was found to have written the statements, troopers said. The student was arrested and taken to the Mat-Su Youth Facility.