The HSE has confirmed that two men have died in Cork in the past 24 hours from suspected intravenous heroin overdoses.
Two others are said to be in a serious condition in hospital.
David Lane of HSE South Addiction Services said were it not for the prompt action of someone alerting the emergency services these two would also have died.
The HSE was unable to confirm that five more people are being treated as a result of the effects of the same batch of heroin.
It said: "While investigations are ongoing into these cases, it is believed that it is possible that they are as a result of a strong batch of heroin which may be in circulation."
The HSE has alerted medical professionals in the region to be on the alert for patients presenting as a result of heroin misuse.
Mr Lane said that it is urging community and voluntary groups working with intravenous drug users to get the message out about the health risks associated with the batch.
He said: “It may actually be more powerful than what they're used to because our suspicion is that there is a purer form of heroin on the streets at the moment.
“So the tolerance levels will not be the same as what people might be used to in terms of their injecting drug use,” he said.
Dr Chris Luke, a consultant from Cork University Hospital, said that the “obvious advice” is “to refrain from injecting any drug” in Cork for the next few days or weeks, especially one that is sold as heroin.
Speaking on RTÉ's Six One News, Dr Luke said that if people insist on injecting drugs, that they must ensure that they do not do so alone, as this is the “most high risk sort of activity you could imagine”.
There is an antidote and it can save lives, Dr Luke said, but it must be administered very quickly.