Murdered Joanna Yeates may have been strangled with her own sock, which was missing when her body was found.

Police are also considering the possibility her killer kept the garment as a "trophy" and have called on the public to call them if they believe they may have seen it.

The plea comes as a Bristol- based forensics expert warned that it could be months before police achieve the breakthrough that could bring the killer to justice.

The detective leading the hunt for Miss Yeates' killer confirmed yesterday that when the 25-year-old's clothed body was found she was wearing only one of her socks.

Detective Chief Inspector Phil Jones said he had not ruled out the possibility the killer may have used the sock to strangle her or that they kept it afterwards.

Miss Yeates' boots and jacket were discovered at her home address in Canynge Road, Clifton, indicating that she had returned home before she died.

The team working on the case, codenamed Operation Braid, has been increased from 70 to 80 officers and the investigation is now one of the biggest in the Avon and Somerset force's history.

The team, which includes scientific, forensic and behavioural experts, is following up more than 1,000 lines of inquiries as members of the public flood the incident room with hundreds of calls.

But a forensic expert from the University of the West of England says it could be several months before police make a breakthrough allowing them to track down Miss Yeates' killer.

Dr Carolyn Morton, a principal lecturer in forensic science at UWE, said anyone expecting the kind of quick result seen in TV dramas such as CSI needed a "reality check".

Landscape architect Miss Yeates was last seen on December 17 after enjoying a drink with work colleagues at the Bristol Ram pub in Park Street. She walked home visiting Waitrose, Bargain Booze and Tesco Express, purchasing a pizza and two small bottles of cider.

Miss Yeates was reported missing by her boyfriend Greg Reardon, 27, two days later when he returned home from a weekend away.

Her body was discovered by dog walkers, partially covered by leaves and snow, on Longwood Lane – three miles from her home – at around 9am on Christmas Day.

Yesterday Detective Chief Inspector Phil Jones stressed he was in charge of a "complex and meticulous investigation that will leave no stone unturned".

He said: "When Jo was found at the site in Longwood Lane her coat and boots were missing. These were later found at her flat in Canynge Road.

"One of her socks was missing and we have yet to find this. It is described as a light grey sock with lighter detail on the toes, heel and shin.

"We have not located this sock at the scene or at Jo's home. I am keen to find it, so I would appeal to anyone who may know where it is to contact my team."

The detective said he was "keeping an open mind" about whether the killer or killers could be keeping the sock, which fits a size 5 foot, as some sort of trophy or whether Miss Yeates was strangled with it.

He told journalists that scientific experts and specialists were helping with the case and that he was "happy" with how the investigation is progressing.

"We continue to use all the professional resources available to us, including accredited experts who are specialists in their fields rather than generalists," he said.

"These resources have been used since the start of what was initially a missing person investigation and now a murder investigation.

"I can assure you that we will find Jo's killer or killers."

CCTV footage from the Hop- house pub of a figure walking up Regent Street which could have been Miss Yeates was published by a national newspaper yesterday. The figure is followed 27 seconds later by two males.

DCI Jones said no footage was being ruled out but that the particular footage was poor and not conclusive.

Shortly after yesterday's appeal a man approached police to offer them a sock, which was placed in an evidence bag.

But police later issued a statement saying the sock was not the one they were trying to trace.

Police yesterday continued to examine bags of forensic evidence removed from the flats belonging to both Miss Yeates and her landlord Chris Jefferies, 65.

Mr Jefferies, a former teacher at Clifton College, was arrested on suspicion of murder last Thursday but released on police bail two days later.

A Facebook campaign advertisement launched on Tuesday has been viewed nearly a quarter of a million times and Avon and Somerset website has received hundreds of hits as a result.

CCTV views on website YouTube have rocketed from 70,000 to just over 120,000 views in a day.

But Dr Morton warned the level of investigation meant it could be months before the vital evidence is found.

She said: "From a forensic scientist's point of view they are trying to find evidence which might identify a person, or indicate contact between people and objects.

"To do this they are looking for evidence that may be microscopic and invisible to the naked eye. It is incredibly time-consuming.

"No two cases are the same. The police pursue many lines of inquiry at the same time and they can get a breakthrough at any moment or it can take a long time.

"Nobody knows what could be the key thing – that vital bit of evidence that may solve the case."

Dr Morton pointed out that 17 months of painstaking forensic work was needed to bring Sarah Payne's killer Roy Whiting to justice. Soham murderer Ian Huntley was only convicted of the murders of Jessica Chapman and Holly Wells after 14 months of meticulous forensics where scientists looked at more than 40,000 fibres, of which only 154 proved vital to the investigation.

Forensic examinations in relation to the murder of Melanie Hall, which remains unsolved, took several months to complete.

Miss Hall disappeared on June 9, 1996, after leaving Cadillacs nightclub in Bath. Her remains were found in a bin bag near a slip road off the M5 at Falfield, near Thornbury, 13 years later.

Dr Morton added: "They may be lucky early on and find something but it may be many months down the line that they have that 'eureka' moment. It may not just be one eureka moment, it might be like pieces of a jigsaw.

"You are looking for links between a victim and someone or something they may have been in contact with and that could be something like a carpet or clothing.

"It really is like a needle in a haystack. Very often the answer is there but the only way is to go through all the hay to find those needles.

"It is very important things are not rushed but done very thoroughly because it is vital not to miss anything.

"It is an enormous job but the nuggets will hopefully be there and the investigators will not stop until they have checked everything.

"We just have to hope they get there. There are very few murders that remain unsolved in the UK.

"Television dramas like CSI don't reflect reality. In reality it's far more complicated, takes much longer and there are no guarantees."

● Police have been accused of censorship after an ITN news crew was stopped from entering yesterday's press conference.

The force complained to broadcasting watchdog Ofcom about a report shown on ITV's News at Ten last night which criticised the investigation.