A 19-year-old has died after taking MDMA at a nightclub in Liverpool.
A man, also thought to have taken the same substance, was taken to hospital but is in a stable condition.
Detective Chief Inspector Simon Vaughan said: "We are urging anyone who took any substances at this location, or anyone who suspects someone has done, to attend their nearest hospital for assessment.
"Likewise, if you are still in possession of any of the described drugs from last night, please do not take them under any circumstances but let us know and we will recover them for further inquiries to be made.
"We also want to hear from anyone who was offered any substances at this location, witnessed the young woman falling ill, were offered or bought the drugs described elsewhere."
Dave Turner is Mixmag's Digital News Editor, follow him on Twitter