Police searching for missing student Libby Squire have admitted "she may have come to some harm".
Detectives made the comments as they released images of clothes like the ones Ms Squire was wearing when she was last seen after a night out in Hull a fortnight ago.
No trace of the 21-year-old has been found since she went missing in Hull, despite extensive searches.
Police said Libby had been wearing a black leather jacket, denim skirt and Vans trainers when she was last seen.
Detective Superintendent Martin Smalley said: "Over the last two weeks, our inquiries into Libby’s disappearance have continued around the clock with detectives and officers working night and day to find her and to understand what happened that night.
"While we do continue to be hopeful and we will always keep an open mind, Libby has been missing for 14 days now and we sadly have to consider she may have come to some harm."
Mr Smalley said: "We are continuing to support Libby’s family through this incredibly difficult and distressing time.
"They are understandably distraught not knowing where their daughter and loved one is, and we will endeavour to give them the answers they desperately need."
Officers said the replica clothing had been donated by Topshop and put together with the help of Miss Squire's mother and her friends.
They said it had been used to help trace her movements on CCTV.
Over the last two weeks, scores of officers have been involved in searches and hundreds of hours of CCTV have been trawled.
Mr Smalley, said: "More work is now taking place behind the scenes rather than in public view, however this does not mean the investigation is slowing or coming to an end, it is exactly the opposite and is very much active and ongoing.
"We are determined and we will do all we can to find Libby - she is our priority."
Mr Smalley said: "While I understand everyone will have questions in relation to the inquiries and searches we have carried out, at this moment in time we are not in a position where we can provide answers without jeopardising the investigation or any potential future prosecutions.
"When and where we are able to, we will provide updates as we fully understand this case has captured the hearts of people not just in the city of Hull, but across the country, and that everyone wants to know where Libby is.
"We will continue with our efforts and our focus to find Libby. I would ask anyone who has any information as to where she may be, to please, consider what her loved ones are going through and to call 101 to help us find her."
It is believed that Miss Squire took a taxi from The Welly nightclub on Beverley Road, Hull, on January 31.
Detectives understand she was dropped off near her home on Wellesley Avenue at about 11.29pm, before a passing motorist offered to help her on Beverley Road.
In footage obtained by ITV News, a man can be seen getting in and out of a car minutes after the philosophy student was last spotted.
The video, which Humberside Police are investigating, shows the unidentified man opening the front passenger door, before getting back inside the vehicle and driving away at around 12.09am on February 1.
On February 6, Pawel Relowicz, of Raglan Street, Hull, was arrested and questioned on suspicion of abduction in connection with Miss Squire's disappearance, and police have said the 24-year-old remains under investigation.
Relowicz was charged with a number of offences unrelated to Miss Squire's disappearance and appeared at Hull Magistrates' Court on Monday.