The Health Service Executive is urging "extreme caution" after eight non-fatal heroin overdoses in Cork were reported to the health service in the past 36 hours.
Analysis by Forensic Science Ireland found a trace amount of a "potent and dangerous synthetic opiod", identified in a light brown powder associated with the overdoses.
The HSE said there is extra risk at this time and strongly recommends people do not try new drugs, new batches or buy from new sources.
Professor Eamon Keenan, HSE National Clinical Lead, Addiction Services, said: "We are urging extreme caution following eight overdoses related to a powder being sold on the heroin market in the Cork region.
"Preliminary laboratory analysis has confirmed that recent overdoses may be caused by nitazenes, a potent and dangerous synthetic opioid. These pose a substantial risk of overdose, hospitalisation and death."
Laboratory tests are under way to identify the substances involved.
