Opioid-related overdose deaths in Massachusetts declined by an estimated 5 percent in the first half of 2017 compared with the same period last year, the strongest indication to date that the state’s overdose crisis might have started to abate.

The state Department of Public Health’s quarterly report on opioid statistics, released Tuesday, showed that 978 deaths attributed to opioids occurred in the first six months of 2017, down from 1,031 in the January-to-June period in 2016.

“The opioid and heroin epidemic has brought tragedy to far too many families, and while the Commonwealth has a lot of work to do, there are some signs of progress in this report,’’ Governor Charlie Baker said in a statement.

Treatment professionals attributed the decline in large part to the widespread distribution of naloxone, the overdose-reversing drug commonly known by the trade name Narcan, which has enabled rescue workers and laypeople to save the lives of people who overdose.

But even as fewer people die, it is not clear whether fewer are overdosing. It’s also not guaranteed that the death rate will continue to decline. And the quarterly report, which also updated fatality figures for 2016, provides continuing evidence of addiction’s toll in Massachusetts: 2,107 dead last year, the highest ever and triple the number in 2013.

“We have a long way to go before we declare victory on this,’’ said Dr. Monica Bharel, state public health commissioner. “We know that ending epidemics takes time and comprehensive effort.’’

Bharel declined to call the reduction in deaths a trend but said she remains “hopeful and encouraged.’’

The data were released just weeks after President Trump said he would declare a national emergency over the opioid epidemic, which claimed close to 60,000 lives across the country last year.

In Massachusetts, opioid-related overdose deaths in 2016 increased by 17 percent over 2015. But that was much smaller than the 31 percent increase in 2015 from the previous year and the 40 percent rise in 2014.

Signs that overdose deaths may be declining emerged earlier this month, when data gathered by district attorneys in Middlesex and Norfolk counties showed decreases of 14 percent and 9 percent respectively. Tuesday’s data from the Department of Public Health strengthened the evidence for a possible shift, with statewide information about deaths confirmed by the medical examiner.

“It’s too early to say we’ve got our arms around this,’’ said Vic DiGravio, chief executive of the Association for Behavioral Healthcare, a trade group for Massachusetts addiction-treatment providers.

Echoing the assessment of other specialists, DiGravio called the death statistics “promising,’’ but he added, “I don’t think we’re out of the woods by any stretch.’’

DiGravio said that treatment providers continue to be challenged by the large number of people using fentanyl and other highly potent synthetic drugs and also by patients who suffer from complex mental illnesses along with their addiction.

While the state has increased the number of detox beds, he said, waiting lists remain for the post-detox treatment programs that can lead to long-lasting recovery.

Kurt A. Isaacson, chief executive officer of Spectrum Health Systems, a large Central Massachusetts treatment provider, said the report indicates “an optimistic trend.’’

“I think we’re seeing the fruits of the labors of a lot of efforts,’’ Isaacson said. “This is a big ship and it’s hard to turn this around, but I think those efforts have had an impact.’’

Baker has made combating opioid misuse a central project of his administration, launching initiatives to limit painkiller prescriptions, educate medical professionals on pain management and addiction treatment, fight the stigma attached to addiction, and expand access to naloxone.

The state has provided naloxone to community health centers and rescue services. The Health Department’s Overdose Education and Naloxone Distribution program, which started in 2007, has trained more than 61,000 people — 14,000 in 2016 alone — to detect the signs of overdose and administer the drug that reverses it.

But the death toll continued to rise month after month — until 2017.

“We know it takes a prolonged, sustained effort to turn the tide of an epidemic like this,’’ Marylou Sudders, secretary of health and human services, said in a statement.

Among other findings in the Health Department’s report:

■ Heroin and prescription opioids have diminishing roles in opioid-related deaths. But fentanyl is on the rise: Among those screened for fentanyl, the powerful synthetic drug was present in 81 percent of overdose deaths in the first quarter of 2017, up from just 19 percent in the third quarter of 2014.

■ In the second quarter of 2017, prescriptions for opioid painkillers declined nearly 28 percent from the first quarter of 2015.

■ While 82 percent of opioid-related deaths occur among white residents, the death rate among Hispanics increased significantly between 2015 and 2016.

■ In the first quarter of 2017, emergency medical personnel administered naloxone on average 1.4 times per overdose. Nearly one-third of people who overdosed required more than one dose of naloxone.

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her on Twitter @felicejfreyer.