Police investigating the "unexplained" death of 18-year-old student Caroline Everest have arrested a man on suspicion of rape.
Sheffield Hallam University student Miss Everest was reported missing after leaving a Sheffield nightclub in the early hours of Sunday morning and her body was found in a river in the city on Tuesday.
South Yorkshire Police said they have arrested a 31-year-old man on suspicion of rape and he remains in custody.
A spokesman said a post-mortem examination on Miss Everest's body has not determined the cause of her death.
Detective Chief Inspector Victoria Short said: "At this time, we are treating Caroline's death as unexplained.
"There have been a number of developments throughout the late evening and overnight as part of this complex investigation.
"A post-mortem examination was completed, however the cause of death was not established and the results were recorded as inconclusive. Further tests have now been requested."
Ms Short said CCTV footage shows Miss Everest leaving the Corporation nightclub, on Milton Street, at around 2.40am on Sunday.
A minute later, she is seen with a man outside the Devonshire Cat pub, which 50 metres up.
The detective said that at 3.35am, CCTV shows Miss Everest and the man parting company in Napier Street, close to where her body was found in the early hours of Tuesday morning.
Ms Short said: "Approximately 10 minutes later, Caroline is seen alone on Summerfield Street, walking in the direction of the river. This is the last we see of her."
She said: "We have carried out extensive inquiries in a bid to identify and locate the man in the earlier CCTV footage. As a result, we arrested a 31-year-old on suspicion of rape. He remains in custody.
"The investigation is ongoing and we continue to review CCTV footage from the information received from the public.
"If you saw Caroline that night, or have any information, I urge you to come forward. Any information, no matter how small, could be vital to piece together her final steps and to provide answers for her family."