A UK-wide attempt by police using DNA to identify a suspect in the case of missing chef Claudia Lawrence has failed.
Detectives travelled across the country trying to match up the sample taken from Miss Lawrence's car.
York chef Claudia, then 35, disappeared on her way to work in March 2009. Officers believe she was murdered.
The DNA sample was found on a cigarette in her car, which was in a garage being repaired when she vanished.
North Yorkshire Police officers had hoped to find a "familial DNA" match that would lead them to a suspect, but they have drawn a blank.
Despite a major investigation and a number of arrests, no-one has been charged in connection with her disappearance.
The case remained open, said the force.
Martin Dales, a spokesman for Miss Lawrence's father Peter, said the family and friends shared police's disappointment "that this very intensive, lengthy and nationwide DNA investigation has on this occasion proved inconclusive".
"They are all appreciative of the continuing work by the police in trying to find Claudia but it is dependent on the quality of intelligence and information that comes to them from the public," he said.
"Someone knows something but the something is being withheld which, after nearly 10 years, is both wrong and cruel to Claudia's family."
Miss Lawrence, from the Heworth area of York, disappeared on her way to work at the University of York.
Her last known contact with anyone was a phonecall to her mother on 18 March 2009.
She failed to attend work the following day and was reported missing.
Det Supt Dai Malyn, who is leading the investigation, has said the team failed to find the breakthrough they were hoping for.
Mr Malyn said: "This is naturally very frustrating for the investigation team and our thoughts are very much with Claudia's family who remain desperate for a breakthrough.
"The family have been updated about the completion of this work.
"As I have said before, the investigation will always remain open and we still receive information on a weekly basis that requires assessment and follow-up."
Police said in January 2017 the line of inquiry relating to a DNA profile would take a further six weeks.
The operation involved obtaining evidence by consent from people who had similar DNA profiles to the unidentified samples recovered during the search.
There was also work done to reconstruct Miss Lawrence's DNA for elimination purposes, the force added.
People who had visited Miss Lawrence's house or been in her car for any reason and had not yet come forward should contact the force, it added.
Claudia Lawrence timeline
- 18 March 2009 The last sighting of Miss Lawrence as she walks back to her house after a shift at work and speaks to her mother, Joan, on the phone
- 19 March 2009 Police are informed of her disappearance after she fails to meet a friend for a pre-arranged drink at a pub
- 25 March 2009 CCTV footage of the chef's last known movements are released
- 24 April 2009 Detectives say they are treating Miss Lawrence's disappearance as a suspected murder investigation
- 6 May 2009 Police reveal they have received more than 1,000 calls about the disappearance and had taken 1,096 statements
- 6 May 2010 Miss Lawrence's father Peter calls for an urgent independent inquiry into the police investigation
- 29 July 2010 Police confirm they are scaling back the number of officers dedicated to the inquiry
- 29 October 2013 Police announce that a new forensic search of Miss Lawrence's home is to begin as they launch a fresh review of the case
- 13 May 2014 A 59-year-old man is arrested on suspicion of murder. He is later released without charge in November
- March-April 2015 Four men are arrested on suspicion of murder and released on bail
- 8 March 2016 Police say the Crown Prosecution Service has decided the four men will not face charges
- 17 January 2017 Police say the review into the case, which has cost £1m, is to be "scaled-down"
- 8 November 2018 Police unable to identify "a possible suspect" after DNA analysis