BELFAST, Maine — Local police are warning heroin users that a pair of drug overdose deaths in Waldo County raise the possibility of fentanyl contamination.

Fentanyl, a synthetic narcotic 50 times stronger than heroin, was linked this month to a surge of drug overdoses in the midwest. The Centers for Disease Control and Prevention on Friday alerted public health departments, health care professionals, emergency responders and others about an increase in fentanyl-related overdoses and deaths in much of the country.

“When you have people addicted to heroin, they pretty much know what a safe dose is for them to take,” Sgt. Nick Oettinger of the Waldo County Sheriff’s Office said Friday afternoon. “When you get people dying who are known drug users that have been in the game for a long time, it starts raising eyebrows.”

Belfast police Wednesday night dealt with an apparent fatal drug overdose of a man in his late 20s. The sheriff’s office was called to Prospect at 5:30 a.m. Friday by the father of another man in his late 20s who also had apparently died of an overdose. Although it is too soon to know exactly what the men had taken or whether it was laced with fentanyl, police said they wanted to alert the public. Neither death appeared to be a suicide, and there seemed to be connections between the batches of drugs found on the scene, police said.

“We don’t have the opportunity to wait the time it takes to get results back from the toxicology tests on the drugs that were found on the scene,” Belfast Police Chief Mike McFadden said. “We don’t have that luxury because we need to inform the public about this because it is so deadly. It may have nothing to do with fentanyl-laced heroin. But the potential is too dangerous to wait, and we want to get it out there. This may be in our community.”

Police are asking anyone with information that could help in the investigation of the two overdose deaths to call 338-2040.