A 21-year-old student who went missing in the early hours of Boxing Day may have been captured on CCTV heading towards the seafront, police said.
Sophie Smith was believed to be wearing only a dark-coloured vest top and light-coloured shorts.
She did not have her mobile phone with her when she left her home in Gorleston, near Great Yarmouth, Norfolk, at around 3am on December 26.
Volunteers have searched beaches in the area for the University of East Anglia student and Norfolk Police said there had been no confirmed sightings of her.
Police Inspector Will Drummond said: "We have diligently searched for Sophie and have investigated a range of scenarios but unfortunately there have been no confirmed sightings or contact since she left her property at 3am.
"We have a possible CCTV image of Sophie heading towards the seafront but, despite all our efforts, we have found no further trace of her."
He said on Thursday that officers had spoken to her friends and family, checked her social media accounts, conducted house-to-house inquiries and liaised with local hospitals.
They also conducted a widespread search, including possible CCTV sightings, and checked places she was known to have links to but nothing has been found.
"I would like to take this opportunity to ask the public to check their sheds and outbuildings in case Sophie has got disorientated and slept in the nearest place of shelter," said Mr Drummond.
"We are in close contact with Sophie's family, who are being supported by officers at what is a very difficult time for them.
"However, due to the circumstances in which she left home with minimal clothing, no mobile phone, her mental state and the weather conditions, the hope of finding Sophie safe and well diminishes as time goes on."
He said Sophie's mother, Lynn Shaw, is grateful for the public's support and assistance but had asked for privacy at this time.
Sophie, who went missing from her home in Avondale Road, is described as white, about 5ft 8ins and slim with shoulder-length blonde hair.
Anyone with information is asked to call Norfolk Police on 101.