NEWTON -- A deadlier than usual batch of heroin is believed to have contributed to a dozen overdoses within the past week, including three fatalities, Sussex County Prosecutor Francis Koch said Friday.

Koch said police officers administered Narcan, a opioid overdose antidote, to all 12 people.

"It is our belief that there is currently an even deadlier batch of heroin, possibly laced with other drugs, being distributed throughout our county, and that is the cause of the increase," Koch told reporters he invited to his office just before 11 a.m. Friday.

Koch, in seeking to put the dozen overdoses in perspective, said Narcan deployments by police in the county average three to four per month.

"That is approximately a 1,200 percent increase," Koch said.

Koch did not provide details on specifics of the overdoses, but said they occurred within the past four to seven days.

"There were on at least one location, at different times, multiple people that received Narcan," Koch said.

Drugs recovered by police have been sent out for testing, Koch said, adding that he suspects fentanyl -- an opioid pan medication described as 100 times more powerful than heroin -- played a role.

"I cannot definitively say (fentanyl) was used in these cases, however I can tell you that this is the kind of reaction that we anticipate if fentanyl was used," he said

Offering some guidance, Koch said, "Today it is even more important than ever that individuals reach out for help, to stop the use of heroin, and to seek assistance," Koch said.

Rob Jennings can be reached at rjennings@njadvancemedia.com. Follow him on Twitter @RobJenningsNJ. Find NJ.com on Facebook.