The number of estimated opioid overdose deaths in Massachusetts continues to rise.

State health officials say an estimated 1,256 people died from opioid-related overdoses in 2014, significantly higher than an earlier confirmed total of 1,047.

The number of deaths in 2015 represents a 57 percent increase over the confirmed 668 deaths recorded in 2012 and a 15 percent increase over the estimated 939 death in 2013.

Department of Public Health officials say the estimated rate of unintentional opioid-related overdose deaths — which includes deaths related to heroin — reached levels previously unseen in Massachusetts last year.

The estimated rate of 18.6 deaths per 100,000 residents for 2014 is the highest ever for unintentional opioid overdoses and represents a 250 percent increase from the rate of 5.3 deaths per 100,000 residents in 2000.