The Oklahoma Bureau of Narcotics is warning of a spike in heroin-related deaths over the past week.
The bureau says seven people have died of suspected overdoses since May 27.
Five of the deaths were in the Oklahoma City area and two of the deaths were in the Tulsa area.
OBN spokesman Mark Woodward says there was a total of 57 heroin deaths in 2018, so seven deaths within a week is concerning.
Woodward says investigators believe the heroin involved in the recent deaths may be laced with fentanyl, a powerful opioid.
The bureau says one arrest has been made in connection with the deaths.