An Italian prosecutor says an autopsy has determined that an American woman, whose naked body was found last week in her Florence apartment, was strangled with an object such as a rope.

Prosecutor Giuseppe Creazzo cautions more time is needed to establish the time of death for Ashley Olsen, a 35-year-old U.S. citizen who had lived in Florence for about three years. Creazzo on Tuesday said results of chemical analyses of body tissue and fluid are needed to narrow the arc of time when she died as well as determine whether she had been sexually assaulted. The autopsy was performed Monday.

Olsen's body, with bruises and scratches on her neck, was discovered Saturday after her Italian boyfriend asked the landlady to open the apartment.