Police say the man who died after taking drugs at a dance event in Manchester had consumed an unknown white powder.
Four of his friends were also taken to hospital.
They've told detectives that they bought their drugs inside the Warehouse Project at the club's opening party.
One woman, who was not with that group and who had bought her drugs elsewhere, was also taken to hospital for treatment after collapsing inside the venue in Old Trafford.
"We believe from the accounts of the gentlemen's friends that they purchased it in the club. Whatever they believed it to be it clearly wasn't, it was dangerous.
"There was a lady as well who was at the same event and we believe she had taken a substance as well but from a different source.
"The message has got to be that whatever it is, you are really dicing with death when you take this stuff. You don't know what it is. We've got two incidents where someone's been seriously ill and in one case someone has died. It really isn't worth the risk."
More top news
People gathered in Manchester Piccadilly Gardens to demonstrate their anger towards the refugee crisis.
Settling down this weekend as high pressure builds
Former Manchester United manager Sir Alex Ferguson has told ITV Sport he twice failed to sign Wayne Rooney before finally getting his man.