PUBLIC health body in the north has issued a fresh alert after several people were admitted to hospital in England suffering effects of a dangerous batch of Ecstasy drugs.
Pills with a similar appearance to those taken by the victims in Britain have been seized in Northern Ireland.
Police confiscated more than 1,200 tablets in Co Derry and made three arrests.
A Public Health Agency (PHA) spokesman said: "The PHA is using its early warning system to raise awareness of the risks of all drug misuse in light of this and is urging those who feel unwell after taking drugs to seek medical help urgently."
People were hospitalised in England after taking yellow tablets marked with a UPS logo. Owen O'Neill, the PHA's lead on drugs and alcohol, urged people not to take risks with their health. "While recent stimulant-related deaths in Northern Ireland have involved pills sold as MDMA which have in fact contained other, more toxic drugs, it is important to remember that pills containing only MDMA can also prove deadly," he said.
Risks from using MDMA include heatstroke, water intoxication caused by drinking too much fluid, and heart failure.
Detective Inspector Andy Dunlop from the PSNI's Organised Crime Branch said: "In recent days police have made seizures of these tablets in Derry and Portstewart - two in Derry and one in Portstewart.
"Three people have been arrested. One seizure in Derry amounted to 1,200 tablets. A number of alerts have been circulated to particular interest groups but we believe it is now appropriate to advise the general public about this risk.
"MDMA is a dangerous and potentially life-threatening drug and there have been well documented fatalities caused by people taking this substance."