The HSE has issued a warning to heroin users in the Dublin region following a number of overdoses on Thursday.
They ask that people avoid buying from new sources and avoid buying new batches of heroin as there is increased risk at this moment in time.
The HSE are advising people not to buy heroin from new suppliers, and to avoid trying new batches or new types of drugs.
People are also warned not to use the drug on their own, and to let people know you are using and where.
If drug users notice they are becoming unwell, they should look out for the signs of overdose and seek medical help immediately.
Prof Eamon Keenan, HSE National Clinical Lead, Addiction Services, said: “We are aware of a number of overdoses occurring in Dublin City today relating to potential new sources of heroin. We are working closely with service providers, An Garda Síochána and the HSE National Drug Treatment Centre Laboratory to obtain as much information on this emerging situation.
“We ask that people are extra cautious during this period while we identify what may be leading to overdoses. We ask service providers to notify their service users who may be at increased risk and help support them to reduce harms during this time.
"We will update services and people who use drugs following analytical confirmation of samples obtained which will help clarify the situation. At present, this issue appears contained to the Dublin City area but we will continue to monitor and update as necessary.”