HAVERHILL — Police recovered fentanyl, a synthetic opioid, from the Haverhill Cooperative Middle School campus late last week.

On Thursday, officers from the Haverhill Police Department were dispatched to the school grounds after a clear bag filled with brown powder was discovered on the walkway just before the front entrance, according to a news release from the department. The substance was identified as fentanyl using rapid response forensic drug testing.

Police determined the incident to be isolated, and there is no further threat to public safety.

The case remains under investigation.

Even in small doses, ingesting fentanyl can be deadly, according to the Centers for Disease Control and Prevention.