A 13-year-old student in Moorhead, Minnesota, was arrested on Thursday after he was found at a middle school with around 1,500 pills that police suspect are laced with fentanyl. 

Moorhead police said staff at Horizon Middle School reported the student had a "large quantity of blue pills" shortly before noon. The teen was detained and the pills were seized by officials without incident. 

Investigators said field testing of the pills showed they are "believed to be" fentanyl-laced counterfeit M30 pills. Further testing is expected.

"This remains an active investigation, and we will continue working closely with Moorhead Area Public Schools to strengthen safety protocols and ensure a secure learning environment for all students and staff," Moorhead Police Chief Chris Helmick said in a written statement on Friday.

The student was taken to the West Central Juvenile Detention Center after he was arrested.