Till receipts found at the flat of Raffaele Sollecito, one of three people suspected of being involved in killing Meredith Kercher, show that he bought two bottles of bleach allegedly used to clean the murder weapon at a time when he claimed to be asleep.

The police are said to be closing in on a fourth suspect, whom they have identified as a drug-dealer from the Ivory Coast whose fingerprints were found on Ms Kercher’s blood-soaked pillow. He lived near the cottage that Ms Kercher shared with Amanda Knox, and was a frequent visitor there.

“We know his name,” one investigator said. The suspect’s DNA was also found in tests on Ms Kercher’s body, suggesting that he took part in the sexual attack and murder.

Police have been rounding up African men in Perugia for “checks” for the past few days. Il Messaggeronewspaper said one hypothesis was that Ms Knox had accused Diya “Patrick” Lumumba, a Congolese bar owner, of sexually attacking and murdering Ms Kercher to cover up for the real killer, to whom she was said to be close.

New witness 'saw Meredith suspects together'

Amanda Knox, Raffaele Sollecito and Rudy Guede were see at the house in Perugia where the American student died

Multimedia

• Murder in Perugia

BACKGROUND

• Meredith Kercher: Q&A

• New DNA not from Meredith suspects

• Timings crucial to Kercher murder investigation

Related Links

• Arrest warrant for fourth Meredith suspect

• Meredith police want tougher charge

Police said that further evidence against Mr Sollecito had come to light in the form of receipts from a shop near his flat for bleach, bought on the morning after the murder and allegedly used to clean an 8in kitchen knife and Mr Sollecito’s Nike trainers. The first receipt was timed at 8.30am on November 2, and the second 45 minutes later, suggesting that the first container of bleach had not been sufficient. The bleach was also used to clean up the flat itself.

Tests have shown Ms Kercher’s DNA on the tip of the knife and Ms Knox’s DNA close to the handle. Police suspect that Mr Sollecito and Ms Knox attempted to clean the knife, failing to realise that they would still leave identifiable DNA traces.

The till receipts call into question Mr Sollecito’s account of events on November 2, since he had testified that he did not get up until 10am, when he was woken by Ms Knox.

He told police that Ms Knox had returned to his flat at 1am but in the morning decided to return to her own cottage to have a shower, taking him with her. They found blood in the bathroom and a smashed window, with Ms Kercher’s door locked. Police believe, however, that Ms Knox and Mr Sollecito smashed the window themselves to simulate a break-in.

Italian press reports at the weekend said that Ms Kercher had often rowed with Ms Knox over her “slovenliness” in the bathroom and her habit of bringing home strange men.

Police have also seized a handbag belonging to Ms Knox, which they believe may have been used to carry the kitchen knife from Mr Sollecito’s flat and back again. They say that this proves “premeditated murder”.

Supporters of Mr Lumumba staged a rally in the cathedral square in Perugia at the weekend to demand his release. No trace of his DNA has been found at the murder scene, and witnesses have testified that he was at his bar, Le Chic. However, Mr Lumumba has still to explain why he deleted a text message sent to Ms Knox on the night of the murder to which she replied “See you later”, or why a signal trace of his mobile phone was recorded in the area of the cottage shortly afterwards. Police expect to recover the deleted message this week.

It has also emerged that one of two mobile phones used by Ms Kercher connected to the internet for eight seconds at 10.15pm on the night of the murder, and that the other received a call five minutes after midnight that was not answered. Both phones were found the next morning.

Giacomo Silenzi, Ms Kercher’s Italian boyfriend, told a Sunday paper that she had been beautiful and innocent. He said that he first suspected Ms Knox might have taken part in the killing as they were waiting to be questioned by police in Perugia as witnesses. He told The Mail on Sunday: “I was on the train heading back to Perugia from my parents’ house when I got a call from Meredith’s other flatmate, Filomena, who told me what had happened. My stomach dropped – I just could not believe it.” At the police station he “couldn’t help thinking how cool and calm Amanda was. Her eyes didn’t seem to show any sadness and I remember wondering if she could have been involved.”

Mr Lumumba, Ms Knox and Mr Sollecito all remain in custody as suspects pending charges.

An Italian judge, meanwhile, has ruled that a further postmortem examination on Ms Kercher’s remains can be carried out. A second examination would delay the funeral of Ms Kercher, whose body has been flown back to Britain.

Times Recommends

• Over the Wall
• Why Africa welcomes the ‘new colonialism’
• Which will come out on top: paper or gold?