Four girls aged 13 are recovering at home after being taken to hospital for symptoms linked to ecstasy tablets, police said.
The youngsters swallowed pink, "teddy bear" pills near the Civic Centre in Wythenshawe, Greater Manchester and were admitted to hospital on Sunday evening.
They have since been discharged and are currently recovering at home.
On Monday night police executed a warrant on a house in Wythenshawe as part of the investigation and continue to carry out inquiries.
Detective Inspector Gareth Davies, from Greater Manchester Police (GMP) said: "This could have caused devastation for several families and, as with any illegal drug, there can be serious or even fatal consequences if you use them.
"We don't know exactly what these particular tablets contain and I would urge you not to take them.
"If you are offered drugs, particularly ones which are a pink and purple colour and have teddy markings on them, then please contact police.
"If you have any information about this incident or have concerns about drugs in the area, I would also urge you to contact police."
Anyone with any information about this incident should call police on 101 quoting incident number 2161 of March 5 2017 or the independent charity Crimestoppers, anonymously, on 0800 555 111.
Photo: Fiona Measham, The Loop