DETECTIVES said "people should be in no doubt" about their determination to find out what has happened to Claudia Lawrence, as five years on from her disappearance, they revealed new lines of enquiry.

North Yorkshire Police last night announced a series of new leads following a review carried out by the force's Major Crime Unit, and confirmed the charity Crimestoppers is offering a £10,000 reward for information that leads to an arrest and conviction.

Miss Lawrence, then aged 35, was last seen alive on the afternoon of Wednesday, March 18, 2009, as she walked home from work at York University.

She did not turn up for her 6am shift the following day and was reported missing by her father, Peter on March 20, 2009.

In a press conference held by North Yorkshire Police on the eve of a Crimewatch appeal, it was revealed a new forensic examination of her house in Heworth, York had uncovered the fingerprints of people who have still not come forward five years after she disappeared.

They also discovered new DNA from samples taken from her home, and the DNA of a male identified from a cigarette butt in her car who has not yet come forward in the investigation.

Investigators are considering a link between this man and an individual identified in the initial investigation as "the left-handed smoker".

He was spotted by a witness smoking with a woman on Melrosegate Bridge at about 5.35am on March 19, when Miss Lawrence would have been walking to work. Neither have ever been traced.

Detective Chief Superintendent Simon Mason, head of crime for North Yorkshire Police was keen to deny reports they had identified a prime suspect in the case, but added: "There are, however, a number of individuals who remain and are of particular interest to this investigation."

Another new line of enquiry to emerge from the review is that Miss Lawrence was spending time in the Acomb area of York in the weeks before she disappeared.

New analysis has found her missing silver Samsung D900 mobile phone was active in the Acomb area in the weeks before she vanished.

Detective Superintendent Dai Malyn, head of the force's enhanced Major Crime Unit, who has led the comprehensive review of the original investigation, said Miss Lawrence used her phone to keep in contact with family and friends "intensively".

But the investigation team believe it was deliberately turned off by someone at about 12.10pm on Thursday, March 19, 2009.

Det Supt Malyn said: "What I would like to know is during this week leading up to her disappearance where has she been going in Acomb?

"Who has she been associating with?"

Miss Lawrence's family came from Darlington, and later moved to Malton, North Yorkshire, where she was brought up.

DETAILS of North Yorkshire Police's new leads will be broadcast on BBC1's Crimewatch at 9pm tonight, when officers are set to release further information.

*Anybody with information that could assist the investigation is asked to contact North Yorkshire Police on 101, select option one, and pass details to the Force Control Room, quoting "Claudia Lawrence".

*Information can also be passed anonymously to the independent charity Crimestoppers on 0800-555111, quoting "Claudia Lawrence, North Yorkshire Police". 

*Peter Lawrence, Miss Lawrence's father, has a dedicated website, Find Claudia

*The Claudia Lawrence appeal is also supported by the Missing People charity