Story highlights

NEW: Man arrested over American woman's death in Florence had met her in nightclub

NEW: Police believe pair had consensual sex at her apartment before she died

NEW: Suspect's DNA was found in Olsen's apartment, and he also had victim's phone

CNN  — 

A man has been arrested in connection with the death of Ashley Olsen, a 35-year-old American artist living in Florence, according to multiple Italian media outlets.

The suspect, Cheikh Tidiane Diaw, was arrested at his home Wednesday night, chief prosecutor Giuseppe Creazzo announced at a press conference.

DNA evidence linked to the suspect was found in a condom and on a cigarette at Olsen’s house, where Diaw’s fingerprints were also found, Creazzo said. Diaw had taken Olsen’s phone and put his SIM card in it, and was using the device when he was arrested, the prosecutor said.

A photograph released by Italian police of suspect Cheikh Tidiane Diaw.

Police believe that Olsen and Diaw, an illegal immigrant from Senegal who was born in 1988, had met at the city’s Montecarla nightclub and left to go back to Olsen’s place together, where they had consensual sex, Creazzo said.

He said Olsen was strangled by something “other than bare hands,” but also had two fractures to her cranium.

Police have established there was no one else present in the room when Olsen died, Creazzo said. Authorities are awaiting the results of toxicology tests.

Florence prosecutor: ‘No one has been excluded’ in death of American

Ashley Olsen and Scout.

Olsen was found dead – apparently strangled with a rope or cord, according to Italian media reports – in her apartment on Saturday. Creazzo told reporters only that it appeared Olsen was strangled with something other than bare hands.

Colivicchi told Italian media outlets that when she opened the door, Olsen was on a bed in a mezzanine loft of the studio apartment. Fiorentini moved her to the floor and performed CPR, she said. Creazzo confirmed in an interview with CNN that Fiorentini tried to revive her.

Olsen’s dog, Scout, who was a regular feature on her Instagram and Facebook feeds, had defecated in multiple places within the apartment, indicating that the well-trained beagle had not been taken for a walk in some time, Colivicchi told media outlets.

Italian media: Ashley Olsen of U.S. may have been strangled with cord or rope

The woman’s friends told investigators they were with Olsen at the Montecarla nightclub in Florence on Thursday night and left her there between 3 a.m. and 4 a.m. Friday, local media reported.

The American’s phone was turned off at about 9 a.m. Friday, police said, adding that they have not found her phone.

Olsen was originally from Summer Haven, Florida. She was living in Florence, where her father, an architect, works at an art school. Her father was seen with friends outside her building Monday, leaving flowers.

“The police haven’t really said anything yet. My son is waiting for the police to share more,” Olsen’s grandmother, Ann Olsen, told CNN by phone from Florida.

Olsen’s friends told CNN affiliate WJAX in Jacksonville, Florida, that Olsen was “full of life.”

“She never met a person who didn’t like her. … She had the best personality,” Staci Kelly told the station, adding that Olsen loved to travel. “She never really stayed in one spot for too long.”

CNN’s Joshua Berlinger, Michael Pearson, Tim Hume, Dana Ford, Vasco Cotovio, Dave Alsup, Allie Malloy and Hande Atay contributed to this report.