ST. PAUL, Minn. (AP) _ Minnesota saw a big drop in drug overdose deaths in 2018.

Preliminary statewide data released Tuesday shows that overdose deaths dropped 17 percent, from 733 in 2017 to 607 in 2018.

Officials say the numbers are promising, but that overdose deaths remain at historic highs and more work needs to be done to prevent and treat substance abuse.

Heroin deaths and deaths involving prescription opioids both declined last year. But deaths related to synthetic opioids _ mainly illegally manufactured fentanyl _ continued to increase. A vast majority of synthetic opioid deaths in Minnesota involved fentanyl.

State Health Commissioner Jan Malcolm calls the turnaround encouraging, and says Minnesota has implemented a ``broad range of efforts to prevent opioid misuse and combat the overdose crisis.''

But Malcolm emphasizes the data is preliminary.