These are the deadly ecstasy tablets - seized in Portstewart recently- that have hospitalised a number of people in England.
The Public Health Agency has issued a warning about the high-strength yellow tablets that contain MDMA and are marked with a “UPS” logo.
Similar pills have been seized in Portstewart and Londonderry with three arrests mate.
The Agency has warned that the drugs could be fatal, and anyone who feels unwell after taking them should seek medical help straight away.
The main three risks from using MDMA are heatstroke, water intoxication caused by drinking too much fluid, and heart failure, a spokesman said.
The PHA is using its early warning system to raise awareness of the risks of all drug misuse in light of the seizures and is urging those who feel unwell after taking drugs to seek medical help urgently.
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.”
Detective Inspector Andy Dunlop from PSNI 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.
“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,” said Owen O’Neill.
Information about illegal drugs can be given to police on the non-emergency number 101, or by calling Crimestoppers .