Last Updated Jan 13, 2016 10:36 PM EST
MILAN -- A Senegalese immigrant was detained Wednesday in the strangulation death of a 35-year-old American woman, just hours after crime scene investigators returned to her Florence apartment to search for clues identifying her killer, reports Italian media.
CBS News has not independently confirmed the report by the ANSA news agency.
The Italian news agency ANSA reported early Thursday that police detained the suspect in Ashley Olsen's murder on Wednesday based on DNA evidence taken from the scene. Investigators had narrowed in on the suspect using video surveillance cameras along the route from the nightclub that showed them together Friday morning, a day before Olsen's body was found. The man was known to authorities for being involved in the local drug scene.
Authorities released no other details. The lead prosecutor had declined to comment on the case earlier Wednesday, and police officials say they are not authorized to speak to media during the investigation.
Crime scene investigators returned Wednesday to the Florence apartment where the American woman was found strangled to death over the weekend, searching for clues to identify her killer.
Ashley Olsen was found nude on her bed in her rented apartment on Saturday after her boyfriend had the owner open the door, alarmed that the young woman had failed to respond to phone calls. The body had bruises and scratches on the neck, and an autopsy determined that she had been strangled with a cord or a rope.
Italian media reports on Wednesday had previously indicated that investigators were narrowing in on a suspect, using video surveillance cameras along the route from the nightclub where she was last seen early Friday to her home, while also searching for clues in the apartment.
The lead prosecutor declined to comment on the case Wednesday, and police officials say they are not authorized to speak to the press during the investigation.
Police have said Olsen's boyfriend, who found her body, has an alibi, and the landlady who entered the apartment with him said he tried to revive Olsen even though it was obvious she was dead.
Olsen, originally from Summer Haven, Florida, had been living in Florence for three years, an active member of the expatriate community and art scene. She had moved to Italy to join her father Walter Olsen, who teaches in the Renaissance art city.
Walter Olsen issued a statement late Tuesday expressing the family's grief and confidence that the killer would be found.
"We are devastated that our precious Ashley has passed away resulting from a horrible and senseless crime," he wrote.
He described his daughter as "a beautiful and creative young woman, with a happy, exuberant and generous soul," adding: "We are heartbroken she was taken from us."
He asked that the family be left to grieve in peace and expressed "faith that the perpetrator will be found and sentenced."
A friend, who would only give her name as Amy, told CBS News the murder was incomprehensible.
"I can't imagine a person who would hurt her, she is a gentle, a kind, a beautiful, friendly, lovely girl and it's an awful shock. We've got a great community here of people, and everyone loved her," Amy said.
Olsen's friends, in a letter appearing in an English-language biweekly in Florence, said they are hoping whoever killed her will be brought to justice.
"While we mourn her passing we place our trust fully in the Italian authorities to investigate this tragic episode," read some of the sentiments in the letter in The Florentine. "We wait to hear what they discover, and pray that justice will be swiftly served to whoever his responsible."
The friends described Olsen as a "rare and kindhearted spirit."
"We have seen the messages of love pour out from her hometown of Florida and we know that, across two countries, people who knew and loved her are in shock," they wrote.
Corriere della Sera newspaper quoted the boyfriend as saying the couple had quarreled over a minor matter three days before her corpse was found, and that he tried to call her but that Olsen didn't answer her phone.
It was unclear when the body might be released for burial, as prosecutors won't give the go-ahead until they are sure more forensic medical testing isn't needed for the coroner's report.