The HSE is warning that a batch of contaminated cannabis may be in circulation in the North East.
It comes as two women in their twenties are being treated in Intensive Care at Our Lady of Lourdes Hospital in Drogheda.
They became critically ill after taking cannabis that may have been mixed with another substance.
The HSE is advising community and voluntary groups working with drug users that reports have been received of unusual side effects.
Gardaí are investigating the matter and a quantity of cannabis has been sent for analysis.