MILAN (Reuters) - Italian magistrates said on Friday they had opened an investigation into possible murder after the mysterious death of a Moroccan model who was a regular guest at former prime minister Silvio Berlusconi’s “bunga bunga” parties.

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.

She told the court one of the parties at the media magnate’s home involved young women, sometimes in pairs, wearing nun’s costumes and stripping off while performing raunchy pole dances.

“They started to dance like the nuns of the film ‘Sister Act’, and then they took off their clothes,” she said. At another party, a woman in her underwear stripped for Berlusconi wearing a mask with the face of footballer Ronaldinho, she said.

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.