Police have issued a warning over a potentially lethal batch of MDMA, which is believed to have already hospitalised seven people.
Four men became seriously ill after consuming the class A drug – known locally as "pink champagne" or "magic" – in Oldham on Saturday evening (24 June).
Two of the men in intensive care, Greater Manchester Police (GMP) said.
On Sunday morning, two further men and a woman were hospitalised after taking what is believed to be the same dangerous batch of MDMA.
The woman and one of the men are in critical conditions, while the other man is in a serious condition.
Police say the drug comes in crystal form and is "highly potent", with many users telling officers it's the first time they've seen or heard of the drug.
Symptoms for those users who may need hospital treatment include rigid muscles, shallow breathing, racing pulse, hyper-aggression/mania, seizure, foaming at the mouth and unconsciousness.
Police say doctors are concerned the batch could end up killing people.
Detective Inspector Jim Faulkner, of GMP's Oldham borough, said: "Following last night's warning, there has been a further three people taken to hospital in bad health after taking what we believe is a form of MDMA.
"This brings the total number of people affected to seven in 24 hours which is causing us no end of concern.
"Please, if you believe that you or somebody you know has taken the drug and begins showing these symptoms then get yourselves to the hospital immediately."
A 26-year-old man has since been arrested on suspicion of supplying Class A drugs and remains in custody for questioning. Enquiries are ongoing.
Anybody with information that could assist the investigation should contact police on 0161 856 9063 or the independent charity Crimestoppers, anonymously, on 0800 555 111.