Imane Fadil, 33, died on March 1 a month after being admitted to a Milan hospital with severe stomach pains. At the time she told friends and her lawyer that she had been poisoned. Her death was only reported on Friday.
“The doctors have not identified with any certainty any pathology which can explain the death,” Milan chief prosecutor Francesco Greco told Reuters, adding that there were “several anomalies” in Fadil’s medical records.
Fadil testified at the 2012 trial of Berlusconi, who was accused of paying for sex with an underage prostitute.
Berlusconi was initially convicted in the case but ultimately acquitted after a judge ruled he could not have known the underage prostitute was in fact a minor.
However, magistrates subsequently laid new charges against Berlusconi and other defendants, accusing them of bribing some of the women who attended the parties to keep them from telling the truth at the initial trial.
They have denied the accusations.
Fadil was never accused of taking bribes. Italian newspapers reported that she was writing a book about her experiences and that the magistrates had obtained a copy of the manuscript following her death.