A fourth person has been arrested in connection with the murder of British student Meredith Kercher in Italy.
Italian police want to speak to Rudy Herman Guede.
Police arrested 21-year-old Rudy Hermann Guede, who is an Ivory Coast national, in western Germany.
He faces charges over the murder and sexual assault on 1 November of Miss Kercher, 21, of Coulsdon, south London, who was found with her throat cut.
Two other men and an American woman who was Miss Kercher's roommate are also being held. They deny any involvement.
Officials said Mr Guede had been arrested in the western German city of Mainz by Interpol on an international warrant.
Police in Mainz said a 20-year-old from Ivory Coast had been arrested for travelling without a ticket on a train bound for Frankfurt.
The man in question appears to be Mr Guede. Perugia police chief Arturo de Felice said he would be extradited to Italy as soon as possible.
Police identified him as a suspect on Monday. They believe he left the central Italian city of Perugia, where the murder happened, for Milan, before travelling to Germany.
Bloody fingerprints found on Miss Kercher's pillow and on toilet paper in her bathroom are reported to match those of Mr Guede.
Local reports said he had been adopted by a family living in Perugia who had since cut ties with him.
The Ansa news agency also said he had played for a basketball team in Perugia, and been popular with foreign students in the town.
Meredith Kercher was a student in Perugia, Italy
Two other men and a woman are being held over the murder of the Leeds University student, whose body was found in her bedroom in a pool of blood.
Amanda Marie Knox, 20, her Italian boyfriend Raffaele Sollecito, 23, and a Congolese bar owner, Diya "Patrick" Lumumba, 38, all deny involvement in the murder of Miss Kercher.
They are all being held in custody in Italy, and under Italian law, they can be held for up to a year.
However, one of Mr Lumumba's lawyers said he expected his client to be released soon.
Mr Lumumba became a suspect based on Miss Knox's police interviews, according to court documents.
No physical evidence has emerged linking Mr Lumumba to the crime scene, and witnesses have placed him at his bar on the night of the murder.
Police do not believe the murder was premeditated, but they allege each of the suspects played a role.
Prosecutors believe Miss Kercher was killed after refusing to take part in an extreme sex game.