The number of fentanyl-related overdose deaths is up sharply in Massachusetts.
State police, which conducts toxicology tests for the state medical examiner, say that fentanyl was present in 336 people who died of overdoses in a 12-month period that ended on Oct. 6.
That's up more than 50 percent from the previous 12-month period.
Fentanyl is a synthetic opioid that is much more potent than morphine and is often mixed with another substance such as heroin.
A report last month from the Centers for Disease Control and Prevention found Massachusetts had the second-highest number of fentanyl confiscations in 2014, with 630 seizures by U.S. law enforcement.
Massachusetts Attorney General Maura Healey has proposed a bill that would make trafficking in fentanyl a crime.
State officials have said there were more than 1,200 overdose-related deaths in Massachusetts last year.