An American woman found dead in her Florence apartment was strangled with an object similar to a rope or a lace, an autopsy has confirmed. Early results from a forensics analysis also indicated Ashley Olsen, 35, did not fight with her killer, as her body displayed no clear signs of struggle, Italian authorities said.

Detectives believe Olsen, from Summer Haven, Florida, knew her attacker as there was no evidence the front door to her flat in the picturesque Santo Spirito district had been forced. Her naked body was found in the apartment with scratches and bruises to the neck on 9 January by her boyfriend, local painter Federico Fiorentini.

The 42-year-old who has an alibi has been questioned by police but is not being treated as a suspect. Witnesses confirmed he was elsewhere when the killing took place, although the exact time of death is yet to be ascertained. Fiorentini told authorities he let himself in borrowing a key from the landlord after growing worried not hearing from her over a few days.

Olsen was last seen alive at the Montecarla cocktail bar not far from her home in the early morning of 8 January. Friends told police she stayed behind at a nightclub after they left.

Nothing was stolen from her flat but police have been unable to find her mobile phone, which might contain vital clues to the murder. The killing could have been witnessed by Olsen's beloved dog, Scout, a beagle, who was found alive inside the flat.

Prosecutor Giuseppe Creazzo said more tests were needed to determine whether the victim, who moved to Florence three years ago to reunite with her father, a professor in the city, had been sexually assaulted.

Police are also examining a black bra found on a bicycle parked less than 20 metres form Olsen's flat as well as her computer and security cameras from nearby streets. The case has attracted comparisons with the murder of British student Meredith Kercher in 2007, because the investigation is being led by the same police chief, Giacinto Profazio.

Raffele Sollecito, who was acquitted of Kercher's murder alongside his ex-girlfriend, Amanda Knox, after a lengthy legal odyssey in 2015, wrote on Facebook about the coincidence. "Oh well, let's give him an award too," he wrote commenting on a link to an article about Profazio's involvement in the fresh investigation.

Some of Olsen acquaintances also expressed hopes that flaws in the Kercher probe will not be repeated. "I would hope for her sake that this investigation is more clear," Georgette Jupe, the author of the Girl in Florence blog, who knew Olsen told AP.