ROME, Italy (CNN) -- A fourth suspect in the killing of a 21-year-old British woman in Italy has been arrested in Germany, Italian police and German prosecutors said Tuesday.
Rudy Hermann Guede was arrested in the German city of Mainz.
Rudy Hermann Guede was arrested by chance after being caught on a train without a ticket by the German authorities in the town of Mainz, near Frankfurt, German prosecutors have said.
Perugia police chief Arturo De Felice said Italian police had known for a couple of days that Guede, 20, of Ivory Coast, was believed to be in the Mainz area.
De Felice told CNN that computer information had traced Guede to Mainz.
The police chief refused to confirm reports in the Italian media that Guede was located after police traced to an Internet cafe in the town messages he had sent on the social networking Web site Facebook.
A spokesman for the prosecutor's office in Koblenz, near Mainz, said the suspect is expected to be deported to Italy in the coming days.
Investigators found the body of Kercher half-naked with a stab wound to the neck on November 2 at her home in Perugia, where she was studying as an exchange student at the Umbrian city's university.
A report issued by an Italian judge last week suggested that the British student may have been sexually assaulted at knifepoint before she was killed in her bed.
Guede was identified after police found a bloody fingerprint on a pillow at the scene of the crime. DNA tests have also linked Guede to feces found in a toilet at the villa Kercher shared with Knox and two Italians.
He was in the same circle of friends as three people taken into custody, a source in Perugia's prosecutor's office said. One of them, Patrick Lumumba, 38, a Congolese bar owner, who denied any involvement, has been released from police custody.
No restrictions have been put on his movements, attorney Carlo Pacelli told CNN: However, he said his client is still under investigation.
De Felice said Guede would not be questioned over Kercher's death until he had been extradited to Italy -- a process the police chief said would take between a week to eight days.
According to reports on the Web site of the British daily newspaper the Daily Telegraph, Guede sent the newspaper an e-mail on Monday saying he planned to give himself up to police.
In a message sent through an account on his Facebook page, Guede said "I know that (I am a suspect)", the newspaper reported.
He added: "The reson (sic) I want to talk with police man, 'cause the news give at me a wrong profile," the newspaper said.
Still being held in connection with the death are Amanda Knox, 20, Kercher's American roommate and Raffaele Sollecito, 23, Knox's Italian boyfriend. Both deny involvement in the killing.
Footage of Guede on the video-sharing Web site YouTube showed him pulling faces.
The video entitled "Boy in Da House" and dated nine months ago shows Guede sitting on a black sofa dressed in a black pullover.
He is seen poking his tongue out at the camera and pulling his ears. His speech is slurred and it is not possible to decipher what he is saying. E-mail to a friend
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