The number of opioid-related deaths in Massachusetts in 2019 remained virtually unchanged from the previous year, according to a report Wednesday suggesting the state may be treading water in the fight against addiction.

The Department of Public Health’s quarterly opioid report tallied 2,023 opioid-related deaths last year, down a mere eight deaths from 2018, in spite of massive investments in treatment since 2015.

And preliminary figures for the last quarter of 2019 raise the grimmer possibility that the number of deaths may be increasing. The state reported 546 confirmed and estimated deaths from opioids in October, November, and December of last year, up 15 percent from the same period in 2018.

Illicit fentanyl remains the main driver of overdoses, found in 93 percent of cases for which a toxicology screen was performed. Cocaine was present in 45 percent of deaths and benzodiazepines (such as Xanax and Valium) in 30 percent.

The peak for opioid-related deaths occurred in 2016, when 2,097 deaths were recorded, and slightly declining numbers in 2017 and 2018 raised hopes that the state may have turned the corner.

In Wednesday’s announcement, officials celebrated that the rate of deaths per 100,000 had declined 5 percent since 2016, in spite of the growing presence of potent fentanyl. But that 5 percent dropoff occurred in 2017 and 2018.

“This report demonstrates that focused investments in substance misuse are having an impact, but there is still a lot of work to do to curb the opioid epidemic in our communities,’’ Governor Charlie Baker said in a statement.

“While we are steadily making progress,’’ said Dr. Monica Bharel, state health commissioner, in a statement, “it is still unacceptable that 2,000 individuals in Massachusetts die from this preventable disease each year.’’

The report also noted that just over 225,000 people received prescriptions for Schedule II opioids in the fourth quarter of 2019, a 42 percent decrease from the first quarter of 2015.

But prescription drugs were found in only 13 percent of those who died, making them a minor factor in opioid-related deaths.

The state’s data show that the so-called “opioid epidemic’’ involves many other drugs. The majority of those who died had multiple substances in their system. This week, the health department’s Bureau of Substance Addiction Services reissued a clinical advisory to substance use treatment providers emphasizing the role of multiple substances in the opioid epidemic.

The state has doubled spending on the opioid crisis, adding more than 1,200 treatment beds.

Felice J. Freyer can be reached at felice.freyer@globe.com.