A man has been arrested on suspicion of the murder of Ashley Olsen, the US woman who was found dead in her apartment in Florence on Saturday, Italian police said.
The man, who was a European, was arrested during the early hours of Thursday "for the crime of aggravated murder of the US citizen Ashley Olsen," the police said in a statement.
It gave no other information.
Florence prosecutor Giuseppe Creazzo said on Wednesday that Olsen, 35, appeared to have been strangled with a cord or rope.
Florence prosecutors will hold a news conference at 0900 GMT to give further details about the arrest.
A police source said on Wednesday that Olsen had been seen in video surveillance cameras walking home accompanied by a man after going to a nightclub on Thursday night.
Olsen had been living in the central Italian art city of Florence for the past three years. Friends said she had moved to Italy to join her father Walter Olsen, who teaches in the city.