North Yorkshire Police has announced a series of new lines of inquiry on the fifth anniversary of the day Claudia Lawrence failed to turn up for work at York University in 2009.
The force launched a review of the investigation last year after a new major crime unit was established by the force.
Claudia was 35 when she was reported missing by her father, Peter, on March 20 2009.
She was last seen at around 3.05pm on March 18, walking back towards her home, and that night she spoke to both her parents on the phone.
Her family believe something happened to her after she left for work early on March 19.
Detective Superintendent Dai Malyn, who is leading the new review of the case, said his team has spent two months re-examining Miss Lawrence's small, terraced home in the Heworth area of York and this work supports that theory.
Police have said before that Miss Lawrence's mobile and rucksack have never been found.
Today they said her hair straighteners also appeared to be missing.
Mr Malyn said: "From the review of all the evidence available, including the fact that Claudia's bed was made and it appears that she had eaten breakfast and brushed her teeth, it is our belief that she had left for work on the morning of Thursday 19 March 2009.
"What is unusual is that Claudia's GHD hair straighteners - model number 14.4.1B and purchased in May 2007 - were missing from her home.
"From our inquiries, it is doubtful that she would take them to work in her blue and grey Karrimor bag which has also never been found."
He said techniques not available in 2009 had uncovered additional fingerprints that need to be identified.
Mr Malyn said: "There is also other DNA material from items examined in the house that have been recovered. Forensic work is ongoing in respect of these items."
He told a press conference at York police station that his team had also found the DNA profile of an unknown man on a cigarette butt in Miss Lawrence's Vauxhall Corsa.
The car was in a local garage at the time of the disappearance but Mr Malyn said the profile did not relate to any man who had yet come forward.
The detective said it was reasonable to consider whether there was a link between this man and an individual spotted by a witness who has been known throughout the five-year investigation as the "left-handed smoker".
This man was seen smoking with a woman on Melrosegate Bridge at around 5.35am on March 19 - when Miss Lawrence would have been walking to work.
Mr Malyn said: "Despite numerous high-profile appeals, neither the man or the woman have been traced. We believe it is important to repeat the appeal for any information that could identify these people.
"In particular, the man who smokes with his left hand could be significant to the investigation in relation to the male DNA profile found on a cigarette butt in Claudia's car."