Undersheriff John Summers says the reservation has had a longtime meth problem but heroin is relatively new to the area.
The Fort Peck Indian Reservation covers most of the county, and authorities say drug dealers often target reservations because of high addiction rates.
The sheriff’s department and police from the reservation and local towns are working to train more officers to administer naloxone, an antidote for opioid overdoses.
The county is also considering reactivating a regional drug task force. A previous task force shut down because of funding problems.