Meredith Kercher was found with her throat cut in her flat in the city of Perugia on November 2.

Italian prosecutors believe she was murdered after refusing to take part in an extreme sex game.

Three people - Miss Kercher's American flatmate Amanda Knox, her Italian boyfriend Raffaele Sollecito and Congolese immigrant Diya "Patrick" Lumumba - have all been remanded in custody over the death of the 21-year-old from Coulsdon, Surrey.

An Italian newspaper reported that forensic traces had been found in Miss Kercher's apartment that suggested a fourth person may have been involved in the killing.

La Repubblica said police had found DNA in the flat's bathroom that did not match any of the three suspects.

The body of the Leeds University student, who travelled to Perugia in August for a year-long study exchange at the city's University for Foreigners, was flown to Heathrow Airport on an Alitalia flight from Rome.

A judge in Perugia said there was enough evidence to hold the trio for up to a year while the case against them was prepared.

There were concerns that the suspects could attempt to leave Italy if they were released - Knox is from Seattle, Lumumba from Congo and Sollecito may have sought his girlfriend's help to flee.

Knox, 24-year-old Sollecito and 38-year-old Lumumba are all being held in connection with the sexual assault and killing of Miss Kercher. All three deny any involvement in her death.