Detectives hunting Joanna Yeates killer refuse to rule out sexual motive

Although there was no evidence that Ms Yeates had been sexually assaulted, Detective Chief Inspector Phil Jones, of Avon and Somerset Police, said they had not ruled out a sexual element to the crime.

He said: "At this stage there is no evidence to suggest that Joanna was sexually assaulted, however I have not ruled out that there might have been a sexual motive."

Speaking at a press conference yesterday, he added: "I can assure you we are determined to solve this crime and bring Jo's killers to justice."

Asked later about his use of "killers" rather than "killer", DCI Jones said he was keeping an "open mind" on the possibility that more than one person was involved in Miss Yeates's death.

Police have also urged the driver of a light-coloured 4x4 seen driving near the spot where her body was found to come forward.

Police said they had received a "number of reports" of the vehicle "driving slowly" near the lane where Ms Yeates's body was found on Christmas Day.

But they revealed the hunt for the car was just one of hundreds of lines of inquiry his team of 70 officers were following up.

DCI Jones said officers had trawled through 293 tonnes of rubbish in the hunt for a missing pizza box at the centre of their murder investigation. They believe the wrapper may hold a vital clue.

Ms Yeates, from Bristol, disappeared on 17 December and her body was found a week later by a dog-walker.

Police have received 1,300 pieces of information from the public, and more than 100 hours of CCTV footage has been watched.

Some 900 lines of inquiry are now being pursued.

DCI Jones said: "We have had a number of reports of vehicles in Longwood Lane during the late Friday evening and early hours of Saturday morning, including a possibly light-coloured 4x4 vehicle.

"This 4x4 and the other vehicles may be completely unconnected, but I urge anyone in that car, or any other driver in the vicinity, to come forward."

He added: "I am satisfied that Jo got back to her flat, but I'm not able to speculate whether she let somebody into the flat, whether somebody was already in there, or whether someone broke into the flat.

"At this time I cannot say where or when Jo was killed, or when her body was left on Longwood Lane."The significant snowfall in the early hours of Saturday December 18 has a considerable impact on this, and I am working with numerous forensic specialists to determine the timings."

The investigating officer said the pizza and the cider that Ms Yeates bought on the night she disappeared remained of interest to the police.

He said it was not clear at this stage whether the landscape architect had eaten the pizza.

Earlier, it emerged that a DNA sample had been retrieved from Ms Yeates's body. Officers hope that the fact her body was found frozen after being dumped in the snow will mean the DNA is well preserved.

Police have admitted the killer was on the loose - and told women not to go out alone after dark.

The stark admission that a murderer "remains at large" came the day after the only person arrested over the crime, Miss Yeates's landlord, Christopher Jefferies, 65, was dramatically released on bail.

Mr Jefferies became the main suspect after it emerged that he had informed police of a possible sighting of Ms Yeates on the evening she disappeared.

Yesterday, he had not returned to his home and is believed to be staying with a friend.

Ms Yeates's boyfriend, Greg Reardon, 27, said he had been uncomfortable with some speculation following Mr Jefferies' arrest.

He described "the finger-pointing and character assassination" as "shameful".

Mr Reardon has now set up a website in aid of the Missing People Charity, which was helpful in the campaign to find Ms Yeates.