Rome - Police made an arrest overnight in the case of a 35-year-old American woman found naked and strangled at her apartment in Florence, Italian media reported on Thursday.
The suspect is a 25-year-old Senegalese man who had been spotted on CCTV alongside Ashley Olsen, an artist and event organiser who had lived in Florence for several years, the daily La Repubblica said.
The Corriere della Sera newspaper described him on its website as "a drug dealer... who knew the victim."
Olsen's corpse was found at her flat in central Florence on Saturday afternoon. She had last been seen by friends at a nearby nightclub in the early hours of Friday.
According to broadcaster Rai and daily La Repubblica, an autopsy also established that Olsen had recently had sex, while witness statements and CCTV footage indicated she had met up with an unidentified man after leaving the club.
Police carried out DNA tests on a condom found in the apartment as well as "biological residues" found on Olsen's body, La Repubblica said.
The case has made the headlines in Italy, with the media suggesting it was the result of an erotic asphyxiation game which went wrong or she was strangled while in a semi-comatose state and unable to resist.
The case followed a lengthy legal saga surrounding another American expat in Italy, Amanda Knox, who was acquitted last year of involvement in the 2007 murder of her British flatmate Meredith Kercher.