The death of university student Libby Squire, whose body was found in the Humber Estuary on Wednesday, is being treated as a "potential homicide", Humberside Police said.
Detective Superintendent Martin Smalley of Humberside Police said: "While we have considered throughout the missing person inquiry that Libby may have come to some harm, Libby's death and the recovery of her body now leads us to solely investigate as a potential homicide.
"The post-mortem examination concluded late last night and at this stage, we will not be releasing any results for investigative and operational reasons.
"We have to protect the integrity of the investigation, which is live and very much active and ongoing, with one man who remains under investigation."
He added: "Libby captured the hearts of not just the people in Hull, but across the country, and as I have said before, the support shown has been overwhelming and my sincerest thanks to absolutely everyone who has been involved."
Libby was last seen at the junction of Beverley Road and Haworth Street at around 12.05am on February 1 while wearing a black denim skirt and faux leather jacket and distinctive trainers, according to police.
Five days later, Pawel Relowicz, of Raglan Street, Hull, was arrested and questioned on suspicion of abduction. He remains a person of interest, police have said.
He appeared before magistrates charged with a number of offences unrelated to Libby’s death and has since been remanded in custody.
Mr Smalley said: "Our thoughts remain today with Libby's family and friends at this incredibly sad and devastating time for them.
"The loss of a loved one is always an upsetting and traumatic experience to go through, but the circumstances surrounding Libby's death will only intensify the heartache for her family.
"Specially trained officers continue in supporting Libby's family and we will do all we can to provide further support and assistance to them in any way we are able to.
"The University of Hull have also created a space for tributes to Libby, which is open to both students and the community to attend and remember Libby and offer any messages of condolence."
Libby who has been described as a popular student who studied philosophy at Hull University, vanished after going out with friends on January 31.
She was dropped off in a taxi near her home on Wellesley Avenue at 11.29pm, and was seen on a bench near Beverley Road around 10 minutes later.
She is believed to have remained in this area until around 12.09am the following day, February 1, but was not seen alive since.
Her disappearance prompted a huge search effort, involving more than a hundred officers and a team of volunteers.
In the hours since her death, a wave of tributes have poured in for Libby, originally from High Wycombe, Buckinghamshire.
The bench on Beverley Road has become a focus for tributes to the student in the hours since the confirmation of her death.
A succession of people laid flowers at the spot on Friday morning, which is just a few hundreds metres from her student home.
One tribute from a nine-year-old girl said: "Gone from our sights but never from our hearts."
Another said: "RIP lovely Libby. Hull will always hold you in our hearts." And one tribute said: "Please don't let one act of hate overshadow the outpouring of love for you."
Almost everyone laying flowers said that they did not know Libby but said they had been shocked and moved by what had happened to her.
A minute's silence was held for Libby during a lunchtime service at Hull Minster where candles have also been lit in her memory.
During the investigation into her disappearance, 24-year-old Pawel Relowicz, of Raglan Street, Hull, was arrested on suspicion of abduction.
He has been remanded in custody, having appeared in court on unrelated charges of burglary, voyeurism, outraging public decency and receiving stolen goods.