Search for missing chef Claudia Lawrence scaled down after police review.
Officers will now only look into any new and compelling information on the missing university chef, who disappeared on 18 March, 2009.
The last person to make contact with Miss Lawrence was her mother, who spoke to her at 8pm on that day.
The 35-year-old – who was not active on social media, did not have a computer or access the internet via her phone – failed to turn up to work at the University of York the next morning.
She was reported missing two days later.
Despite significant publicity, several arrests and a lengthy police hunt, no one has ever been charged over her disappearance.
She is presumed to have been murdered, though her body has never been found.
There is currently on outstanding line of inquiry relating to DNA profiling, which will take a further six weeks to finalise.
Unless that provides a breakthrough the probe will be scaled down next month, North Yorkshire Police have said.
The force said Miss Lawrence’s parents Peter and Joan and sister Ali had been told the news.
It said several new lines of inquiry had been pursued by detectives with vigour and determination.
The force said in a statement that despite exhaustive efforts, as well as the support of national experts and the application of the very latest forensic techniques to exhibits recovered many years ago, it had sadly not been able to find that crucial piece of information.
Officers also said the investigative team had traced and spoken to many people who did not come forward in the first inquiry.
A revision of the original investigation was launched in 2013, with officers reviewing CCTV, mobile phone records, DNA samples, 4,100 exhibits and more than 400 fingerprints.
Four men were arrested two years later on suspicion of murder, but the Crown Prosecution Service decided there was insufficient evidence to charge them.
Detective Superintendent Dai Malyn said he and his team shared the Lawrence family’s frustration that officers had been unable to prove what happened to Claudia, or to find her.
It is not for the want of trying that a breakthrough has not yet come, but rather the result of the continuing refusal of those who know what happened to Claudia to come forward and tell us the truth, the force said.
It asserted the case will not be closed until those responsible for Claudia’s disappearance and, we believe, her murder, are brought to justice.
Disappointing news though this is for Claudia’s family, we have not given up hope, and I do believe that one day we will be able to tell them what happened to Claudia, it added.
Martin Dales, a spokesman for Peter Lawrence, said his friend was depressed and saddened by the move, but believed there was always hope while there remains no explanation for his daughter’s disappearance.