Sources tell 9NEWS the teen is currently on a mental health hold.
Westminster Police spokeswoman Cheri Spottke told 9NEWS Crime and Justice Reporter Anastasiya Bolton police were notified of the threat Friday. 9NEWS has learned the threat was verbal.
Spottke couldn't get into the specifics of the threats because of the open and on-going investigation. For the same reason, she couldn't say if any weapons were found on the student.
Spottke said the teen was not in police custody, but authorities do have an arrest warrant for him. It's not clear when he will be taken into custody.
"He's not a danger to the school or the community," Spottke said.
Jefferson County School Spokesperson Lynn Setzer said the boy just started at Moore Middle School. He transferred from another school.
The teen is expected to face charges of interfering with a school official.