Joana Burns, 22, fell ill on a night out at The Foundry in the University of Sheffield's Students' Union building on June 6.
The Sheffield Hallam University student, who had just completed a degree in mathematics, was rushed to hospital but died the following day.
She had taken MDMA - a form of Ecstasy - on the night out.
Two men, aged 23 and 24, and one woman, aged 20, were arrested suspicion of supplying drugs and were released under investigation.
A South Yorkshire Police spokeswoman said: "Enquiries remain ongoing in relation to the investigation and those arrested remain released under investigation at this time."
An inquest into the death has been opened and adjourned.