The Sun newspaper has offered a £50,000 reward for information leading to the conviction of the killer of Joanna Yeates.
Detective Chief Inspector Phil Jones said he hoped the offer of money would lead to someone coming forward.
“It demonstrates the level to which the murder has touched the nation – and the commitment of the media in supporting our efforts to bring whoever is responsible to justice,” he told the newspaper.
“I’m sure someone out there has that vital piece of information we need to catch Jo’s killer.
“I would urge anyone with any information to come forward and help us find the answers both ourselves and Jo’s family want and need.”
Meanwhile, a leading criminologist has told Sky News police probably know more about her killer than they are letting on.
Professor David Wilson, of Birmingham City University, said he believes police have already narrowed down the hunt to a small pool of suspects.
He said it was extremely likely Yeates knew her killer – and said detectives would now be relying on forensic evidence to rule people in or out.
“It’s forensic evidence that will lead to the killer in this case, not a Cracker-like profiler,” Wilson said.
“If I wear my hat as a profiler, though, I would say the strongest theory is that the perpetrator and victim know each other.”
Wilson said despite reports police had recently employed the services of a profiler, such a move would probably be used as a formality by officers looking to “cover all the bases”.
And in other news, an ITV film crew was stopped from entering a press conference about the case on Wednesday.
Police complained to broadcasting watchdog Ofcom about a report on ITV News at Ten on Tuesday night which criticised the way they were handling the investigation.
A police spokesman accused the report of being “naive and irresponsible”.
“A live murder investigation has been under way now for just twelve days and the media have played an important role in helping us to appeal for witnesses,” the spokesman said.
“While we appreciate the support we have received so far from most of the media we must step in if we feel coverage will hamper the investigation. Our primary aim will always be to secure justice for Joanna.”
It is not known if ITV crews will be allowed into future press conferences.