ENGLISH architect Joanna Yeates may have been killed by more than one person, a detective leading the inquiry revealed last night.
Detective Chief Inspector Phil Jones said one "hypothesis" is that an accomplice helped whoever strangled the landscape architect, adding that he was "not making any assumptions" about how the crime was committed.
Crime officers continued to search the home of Christopher Jefferies (65) -- the former English teacher who owned Ms Yeates's flat in Bristol and lived in the same building -- 48 hours after he was released on bail.
Mr Jones said Mr Jefferies, the only person so far arrested on suspicion of Ms Yeates's murder, "is still a suspect" but refused to say whether any other suspects have been identified.
He also disclosed that witnesses had reported seeing a light-coloured 4x4 vehicle near the spot where 25-year-old Ms Yeates's body was found on Longwood Lane, around three miles from her home in Bristol.
Mr Jones added: "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."
Appealing for help in finding the 4x4, he 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 that night to come forward," he said.
Speaking during a press conference, he revealed that there were still significant gaps regarding Ms Yeates's final hours. "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," said Mr Jones.
Mr Jones also raised the possibility of there being more than one person responsible when he said: "I can assure you, we are determined to solve this crime, and bring Jo's killers to justice."
When asked about this comment later, he said: "I think that phrase emphasises that I am not making any assumptions in this case."
DCI Jones also revealed the huge amount of information detectives were sifting through as the investigation entered its third week.
He said the pizza and the cider that Ms Yeates bought on the night she disappeared remained of interest to police.
Officers have searched through 293 tonnes of domestic rubbish to find the pizza, and said it is not clear at this stage whether the landscape architect had eaten it.
"This is potentially a long and complex inquiry, involving over 70 police officers and staff.
"No stone will be left unturned in this investigation."
He said the police had received more than 1,300 pieces of information, and 900 lines of inquiry have been generated, of which 239 were classed as "high priority".
Police have warned women not to walk home alone after dark following the discovery of Ms Yeates's body.
Ms Yeates was last seen on the evening of Friday, December 17 after she had been in a pub with colleagues. Her body was found by a passerby out walking a dog in Failand, North Somerset, on Christmas Day. She had been strangled.