A new killer drug combination has been unleashed on Long Island and authorities said it had already claimed the lives of at least nine in Nassau County during the first three months of 2017 — with the results of toxicology reports from “several more fatal overdoses” pending to determine if there were more victims.

The spike in deaths linked to the new “potentially lethal mix” of fentanyl and cocaine caused Nassau County Executive Edward Mangano to issue a public warning Friday, alerting residents to the dangers of the new killer drug and reminding them of a 24/7 hotline they could call for help and support.

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“Fentanyl places the person overdosing and the rescuer in danger if they come into contact with this potent drug, which can be harmful if absorbed into the skin, or accidentally inhaled,” Mangano said in a statement, adding: “If you or a loved one is addicted to drugs, get help before it’s too late — call our 24/7 Help Hotline at 516-227-TALK.”

Mangano said fentanyl was “easy and inexpensive to make,” adding that drug dealers had increasingly been using it to spike heroin and to create counterfeit versions of such drugs as oxycodone or Xanax. While circumstances surrounding fatal cases in Nassau remain unclear, the statement released by Mangano said, analysis of drug seizures in the region “confirm the presence of fentanyl in some seized cocaine samples.” It is likely that the users were unaware of the presence of fentanyl, the statement said.

Of the 190 opioid overdose deaths recorded in Nassau in 2016, the Nassau medical examiner’s office found 67 were caused by fentanyl — a dramatic rise from the 22 fentanyl deaths recorded in Nassau in 2015. It was the first year for which statistics were recorded that fentanyl deaths surpassed the number of heroin deaths in Nassau, authorities said. There were 53 heroin deaths in Nassau in 2016. There have already been 17 fentanyl-related deaths recorded in Nassau in the first three months of 2017.

Deaths from pure heroin or from oxycodone, meanwhile, appear to be decreasing in Nassau in 2017, Mangano said.