An Italian judge has ruled that the three suspects in the murder of Meredith Kercher, the British student who was found dead a week ago, can be held in custody for up to a year, pending charges.

Claudia Matteini, the judge, said that there was sufficient evidence in the case to hold the trio and that there was sufficient risk that the two foreign suspects, Amanda Knox, an American, and Patrick Diya Lumumba, a Congolese immigrant musician and bar owner, could flee the country.

Under Italian law, the three can be held in custody for up to a year before charges are brought.

Ms Matteini yesterday questioned Mr Lumumba, who has been in prison with the two other suspects since their arrest on Tuesday.

Mr Lumumba claimed that he could prove that he was not involved in the murder and had not even been present at the "house of horrors". He said that he would call 16 witnesses who would swear that he was at Le Chic, the bar he owns in Perugia, until one in the morning.

In a separate development, Italian press have reported that an unnamed man approached police saying that he received a text message before Ms Kircher's death saying that she "must die". Police have confirmed that a man has contacted them, but did not identify him or say who had sent the alleged message.

"I can also provide till receipts with the time on them, and I was the only person on the till that day" Mr Lumumba told the judge, according to transcripts in the Italian press. He added: "I swear I have never entered the house of horrors, and I was not there that evening, or the day after. I have never been there".

He claimed that after closing the bar he had gone home to sleep, as his Polish wife, Alessandra, would confirm. Asked if he had known Ms Kercher, he said that he had, but had not met her often, let alone had a relationship with her. He said that he knew Ms Knox, a student from Seattle at the centre of the murder mystery, "because she worked for me in the bar twice a week, on Tuesdays and Thursdays".

Ms Kercher was killed some time between midnight and two in the morning at the cottage she shared with three other women, according to the police pathologist. Mr Lumumba said the witnesses who could vouch for his alibi included a university professor, a Senegalese man and two young women, one Belgian and one American.

Ms Knox has testified that she met Mr Lumumba last Thursday evening and that they went to the whitewashed cottage she shared with Ms Kercher and two Italian girls. She claims that Mr Lumumba "wanted" Ms Kercher, that the two of them went into Ms Kercher's bedroom, and that she had heard Ms Kercher screaming but did not intervene.

Police found a text message from Ms Knox to Mr Lumumba on Thursday evening saying "See you later", implying that she and Mr Lumumba had arranged to meet.

Mr Lumumba told the judge, however, that this was not an assignation but rather a general greeting on the lines of "See you around". He said Ms Knox's message had been in reply to one from him telling her not to bother coming to the bar to help out because there were few customers and it was a quiet night.

Mr Lumumba said he knew Raffaele Sollecito, Ms Knox's Italian boyfriend, but only by sight "because he used to come and pick Amanda up when she finished work".

In his own testimony to the judge, Mr Sollecito said he had spent the evening and night of the murder at his flat, but could not remember whether Ms Knox was with him the whole time because he had smoked marijuana and his memory was hazy.

Asked about the knife found in his possession, which police say is "compatible" with the weapon used to cut Ms Kercher's throat, Mr Sollecito said he was still so befuddled when taken in for questioning that he had forgotten to take it out of the pocket of his jeans.

Corriere della Sera said forensic tests at the cottage had shown "no traces" of Mr Lumumba, which supported his contention that he had not been there.

A footprint in blood was however "compatible" with the Nike trainers owned by Mr Sollecito. Witnesses have said they saw Ms Knox and a "North African" man washing clothes and a pair of Nike trainers at a launderette the day after the murder. "The hunt is on for a fourth person" said La Stampa, noting that "someone cut Meredith's throat".

Ms Knox's lawyer said that, unlike Mr Lumumba and Mr Sollecito, his client had exercised her right not to reply to the judge's questions. Instead, she was writing her own version of what happened in her cell.

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