A forensic team is beginning a new search of the home of missing university chef Claudia Lawrence as detectives launch a fresh review of the case.
The 35-year-old was reported missing four-and-a-half years ago after she failed to turn up for work at York University.
Despite a high profile investigation by North Yorkshire Police involving up to 100 officers, no trace of Miss Lawrence has ever been found.
Detectives have stressed that the new review of the case has not been prompted by any important fresh lead.
Miss Lawrence's family has mounted a high-profile campaign to keep the case in the headlines and her father, Peter Lawrence, welcomed the move.
Solicitor Mr Lawrence told BBC Breakfast: "Without being too hopeful, it does give you some hope. There have been advances. They are able to look at this afresh and any opportunity at all to find out for the family and for friends what happened to Claudia is obviously to be welcomed."
Miss Lawrence's terrace house in the Heworth area of York has not been lived in since she failed to turn up for work in March 2009 and was not seen again.
Her father said police had exclusive possession of the house for 18 months and it had been left since then.
Asked how the house is, he said: "It's feeling sad, if I can describe a house like that. It's not been lived in for four-and-a-half years."
Police said one of the reasons they are searching the house now is due to the possibility that it could be occupied again in the future.
Mr Lawrence said: "There must, as we know, still be somebody out there. If this new investigation sparks somebody's conscience, the family really need to know."
North Yorkshire Police have always said they believe Miss Lawrence has been murdered but no body has ever been discovered.
The new search of the house where she lived alone in Heworth Road, York, follows the formation of a new major crime unit at the North Yorkshire force.
Detective Superintendant Dai Malyn, who heads the major crime unit, said: "There's no new smoking gun or startling piece of evidence. I wouldn't want people to believe that's the case.
"This is just part of the review process."
Mr Malyn said the search, which could last a fortnight, was the beginning of a review as part of the new team's remit to look at important cold cases.
"Most cold case review work considers forensic re-evaluation as techniques advance and this case is no different," he said.
"I am also mindful that, at some point in the future, the house may become re-occupied and these opportunities would otherwise be lost."
The detective said forensic science was evolving and he hoped advances since 2009 might assist with his review.
He said there was nothing in Miss Lawrence's home that prompted the decision to search it again.
"Originally the house was tidy and didn't appear to have any sign of disturbance," he said.
"But that's not to say you can't do something in a house, then tidy it up to make it look as if everything was ordinary. These are the things that we'll be looking at."
Miss Lawrence was last seen by work colleagues on Wednesday March 18 2009, when she finished for the day. She spoke to both her parents on the phone later that night and appeared to be normal.
Detectives have said in the past that they believe the key to the inquiry is her relationships with a number of men - relationships a previous head of the inquiry described as having an ''element of complexity and mystery to them''.
Mr Malyn said: "As ever, we will afford anyone who contacts us our full attention if they think they have information which could assist - no matter how small or irrelevant they think that information might be.
"It is never too late for people to come forward with information now that, for whatever reason, they felt unable to share with us in the past."