COLORADO SPRINGS, Colo. (AP) — Two 13-year-old boys are under arrest for allegedly plotting to kill people at their middle school in Colorado Springs.

Sabin Middle School (credit: CBS)

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Police said Monday the boys were arrested following an investigation that began Wednesday when officers responded to “suspicious circumstances” at Sabin Middle School.

Investigators say the boys made threats to hurt staff and students at the school.

(credit: CBS)

Police spokesman Lt. Howard Black said investigators learned the students had established a “kill list” and were messaging each other discussing how to carry out their threats made against staff, students and property.

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Lt. Howard Black with the Colorado Springs Police Department (credit: CBS)

Parents of those mentioned on the list were notified.

Investigators say guns were recovered as part of searches done during the investigation but didn’t disclose details.

Police don’t believe the two boys are the only ones involved in the alleged plot.

The boys are now in a juvenile detention center.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)