Police made an urgent appeal on Monday in the wake of a teenage girl's death after she took a "MasterCard" ecstasy pill.
The youngster's death is being investigated after officers were called at around 5am on Monday to the Victoria Warehouse on Trafford Wharf Road in Trafford, Greater Manchester.
Now police are urging anyone else who took the pill to seek urgent medial attention.
"We are appealing to anyone who may have taken this form of ecstasy, known as 'MasterCard' to get checked out urgently", a police spokesperson said.
"Even if you took it some hours ago, this pill will still be in your system and could be seriously harming your health".
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A 16-year-old boy is said to be in a serious condition in intensive care after taking what may have been a 'Mortal Kombat' ecstasy pill, police said.
Tests are also being carried out on a 17-year-old boy after both teens became ill following a house party in Coatbridge, North Lanarkshire, yesterday.
The pair were taken Monklands District General Hospital in Airdrie at about 11.30pm having apparently taken illegal drugs.
Police Scotland say they believe the drugs included ecstasy and "possibly" a Mortal Kombat tablet.
A NHS Lanarkshire spokeswoman said: "Anyone who has taken ecstasy - particularly the one described as 'Mortal Kombat', and who is feeling unwell, or who knows someone who has taken this type of drug in the past few hours, should attend or contact their local hospital for treatment and advice."
Police Scotland has issued posters warning festival goers of the recent deaths linked to fake ecstasy pills:
There are pills of different colours & designs being sold as ecstasy in Scotland that are toxic. People have died. Don't Risk It! #titpinfo
The poster warns, "These or other dangerous drugs may be circulating at this festival".
"Be Safe. Don't risk it", it adds.
Police in Northern Ireland are working to establish whether fake 'Rolex' ecstasy drugs, thought to be linked to the death of seven young people in Scotland are the same ones suspected to be responsible for a number of sudden deaths in Belfast.
It had been feared that 8 unexplained deaths of people in their 20s and 30s over the past month in Northern Ireland had been caused by the same batch of drugs, however police said no single drug was responsible.
PSNI officers told UTV they were liasing with officers across the UK, and in the republic of Ireland.
Police in Scotland were keen to send out a warning on ecstasy ahead of this weekend's T in the Park music festival.
Seven deaths have been linked to fake ecstasy pills being circulated across Scotland, with an 18-year-old woman dying after taking the tablets.
Drug "amnesty bins" will be available at the entrance to the campsites in Balado, Perth and Kinross where illegal substances can be disposed of without risk of prosecution, police said.
Chief Inspector George MacDonald said: "We want to encourage people to enjoy themselves but our priority is keeping people safe and we want to make them aware of the direct dangers of becoming involved with drugs."
Police Scotland's Superintendent Grahame Clarke said the fake ecstasy tablets that have been linked to the deaths of seven people are a "real concern" and "could contain a cocktail of toxic ingredients".
An investigation is under way and our inquiries have so far revealed that the woman, along with three friends, had taken what they thought were ecstasy tablets. The tablets were described as green with a Rolex crown logo stamped on them.
Public warnings have been issued recently in relation to the dangers of taking ecstasy, or indeed tablets being passed off as ecstasy. They are illegal and could contain a cocktail of toxic ingredients.
We have yet to establish if this particular pill is to blame for the death of this young woman, but the fact that she and her friends took pills described as green and with a Rolex stamp on it causes us real concern.
The exact contents of the pills are unknown but they could contain dangerous chemicals and users need to be aware of the dangers and understand the devastating effect they can have.
A teenager has died after taking a fake ecstasy tablet - the seventh reported death in Scotland linked to the pills.
The 18-year-old woman died yesterday in Alexandria, West Dunbartonshire, and three of her friends were admitted to hospital after taking the pills.
The tablets circulating in Scotland contain toxic chemicals with potentially fatal effects, Police Scotland said.
The pills are green and stamped with a crown logo and some have been found to contain a dangerous stimulant Methoxyamphetamine, known as PMA, police said.
They are also warning of a white pill with the Mitsubishi logo imprinted on it, found to contain the chemicals 5IT or AMT, and a yellow tablet with a star logo.