Prosecutors say there are no external signs of a sexual assault against Ashley Olsen, but more lab results are needed.

An American woman whose naked body was found last week in her apartment in Florence was strangled, according to a post-mortem examination.

Italian prosecutors said an object such as a rope or cord was probably used to kill Ashley Olsen.

They said more lab results would be needed to pinpoint the exact time of the 35-year-old's death, which could take weeks.

Autopsy findings indicate that Ms Olsen, who had been living in Florence for about three years, died in a 36-hour-period between the morning of Friday and the early afternoon of Saturday.

Her body, with bruises and scratches on the neck, was discovered when her Italian boyfriend asked the landlady to open the apartment door after he had not heard from her in a few days.

Ms Olsen, originally from Summer Haven, Florida, was last seen by friends early on Friday at a popular Florence nightclub.

Prosecutor Giuseppe Creazzo there were no external signs of sexual assault, but lab results would also help establish whether she had suffered such an attack.

Mr Creazzo said investigators have no suspects at this point.

Italian news reports say police have not found Ms Olsen's mobile phone.

Her father teaches in Florence, and her social circles included the art community in the Tuscan capital, renowned for its Renaissance architecture and masterpiece-rich museums and churches.

Corriere della Sera newspaper quoted the boyfriend, an artist, as saying the couple had quarrelled over a minor matter three days before her body was found.

He said he tried to call her, but she didn't answer her phone.

Ms Olsen was known around the local area for often being seen with her beloved beagle, Scout.

Her 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 the letter in The Florentine.

The friends described Olsen as a "rare and kind-hearted spirit".

Source: Sky News