Tests are still being carried out to determine why exactly a Sheffield student died after taking drugs on a night out.
Joana Burns, aged 22, who had just completed a degree in mathematics at Sheffield Hallam University, died after taking MDMA - Ecstasy - on a night out with friends last month.
She had been at The Foundry in the University of Sheffield's students' union building when she fell ill and later died.
Friends told South Yorkshire Police that they had each paid £7 for the drug before they got to the venue and that it was supposed to have been a 'final fling' before they left university.
Another student - a 20-year-old woman - took drugs at The Foundry and also fell seriously ill.
She remains in hospital, where her condition is now described as stable.
Sheffield Council is due to carry out a review of The Foundry's licence tomorrow following concerns raised by South Yorkshire Police about the supply and use of drugs at the venue.
Detective Sergeant Andy Shields, of South Yorkshire Police, said: “I want to make it clear that while we believe these incidents may relate to the consumption of drugs, a post mortem examination was unable to determine a cause of death.
“Further tests, including toxicology, are being carried out.
“Three people have been questioned in connection with our ongoing inquiry and have been released under investigation.
"This remains an active investigation and we will continue to pursue any and all lines of enquiry to ensure we understand the full circumstances surrounding one woman’s death and another woman’s illness.
“I’d ask people not to speculate about these matters but if anyone does have any information that they feel might help officers, to get in touch."
Call South Yorkshire Police on 101.