MISSING Joanna Yeates, whose snow-covered body was found on Christmas Day, had been strangled, police revealed yesterday.
The 25-year-old landscape architect died as a result of "compression of the neck" and a murder inquiry has been launched.
Det Chief Insp Phil Jones, who is leading the investigation, said he believed Miss Yeates's body had been dumped "several days" earlier.
The officer said a number of lines of inquiry were being pursued, including the possibility there was a sexual motive behind her killing or that the graduate knew her killer.
Police are also keeping an "open mind" over whether Miss Yeates had been held captive or had been killed where she was found.
Det Chief Insp Jones said Miss Yeates's boyfriend Greg Reardon, who reported her missing on Sunday night after returning to their Bristol home from a weekend away in Sheffield visiting family, was being treated as a witness and not as a suspect.
He said: "The investigation into the death of 25-year-old Joanna Yeates is now a murder investigation. The pathologist completed his examination and concluded that the cause of her death was compression of the neck – in other words, strangulation."
Miss Yeates had been missing for eight days when her clothed body was discovered in Longwood Lane, Failand, North Somerset, by a couple walking their dogs close to the Bristol and Clifton Golf Club, about three miles from her home.
Det Chief Insp Jones said: "I am keen to hear from anybody who saw or heard anything or anyone acting suspiciously in the Longwood Lane area particularly the area near to the entrance of Durnford Quarry over the last week but in particular the weekend of Friday, December 17, to Sunday, December 19 – this was the weekend when we experienced heavy snow in the area.
"However small or insignificant you think your information might be, please come forward and speak to us."
Forensic officers were yesterday continuing the meticulous search of the Failand area and police were also examining Miss Yeates's flat in Canynge Road for signs of a struggle.
Miss Yeates was last seen alive on the evening of December 17, having bought a pizza at Tesco Express in Clifton at about 8.45pm.
Police believe she then walked the short distance home to the ground floor flat she shared with her boyfriend because her keys, purse and bank cards were found there, together with a receipt from Tesco.
Earlier that night she had been drinking with work colleagues at the Ram public house in Park Street. Miss Yeates left there at about 8pm and while walking to Waitrose on the Clifton Triangle phoned her friend Rebecca Scott to arrange to meet on Christmas Eve.
Det Chief Insp Jones said: "We also know that she went to the Bargain Booze shop and a Tesco Express store in Regent Street, Clifton, where she bought a pizza, leaving that store at about 8.30pm.
"At the time she would have arrived home, which would have been approximately 8.45pm, there were other pedestrians and vehicles in Canynge Road.
"We would like anybody in the area of Canynge Road to please come forward."
On Monday, Miss Yeates's parents David, 63, and Theresa, 58, brother Chris, his partner and Mr Reardon, 27, made a heartbreaking visit to where her body was found to lay flowers.
"I do, of course, offer them my heartfelt condolences as this tragic time," Det Chief Insp Jones said. "Somebody out there does know what happened to Joanna. Somebody out there is holding that vital piece of information we need to help provide Joanna's family with the answers they need and want.
"What we have to do next is find out why she was killed and who was responsible. I have a large team of police officers and staff who have been working tirelessly to help find the answers to those questions."
Anyone with information is asked to contact police on 0845 456 7000 or Crimestoppers on 0800 555 111.