An Italian prosecutor has opened an investigation into how Facebook allowed the publication of insults and bullying posts aimed at a teenager who later leapt to her death from her third-floor bedroom window. Carolina Picchio, 14, from Novara in northern Italy, died in January after a gang of boys circulated a video on Facebook of her appearing drunk and dishevelled in the bathroom at a party.

The group, aged between 15 and 17, were said to be friends of Miss Picchio's ex-boyfriend. He had allegedly insulted her on Facebook when she left him days earlier. In a note to the boy found in her room, Miss Picchio wrote: "Isn't what you have done to me enough? You have made me pay too many times."

The boy said he apologised to her for the insults, but she then took her own life, writing on Facebook: "Forgive me if I am not strong. I cannot take it any longer." The Italian Parents' Association has already filed a criminal complaint in Rome directly against Facebook for allegedly having a role in the instigation of Miss Picchio's suicide.

"This is the first time a parents' group has filed such a complaint against Facebook in Europe," said Antonio Affinita, the director. "Italian law forbids minors under 18 signing contracts, yet Facebook is effectively entering into a contract with minors regarding their privacy, without their parents knowing." Francesco Saluzzo, the Novara prosecutor, said he did not rule out placing Facebook staff under investigation. Mr Saluzzo said he was investigating how the video had stayed online "for days", even after Miss Picchio's friends requested its removal.

"There is a procedure for asking for the removal of messages that break rules," he said. "This is an open investigation without named suspects, as yet. Facebook itself is not under investigation. But we could theoretically investigate employees of Facebook who failed to respond to these requests." Mr Affinita said Miss Picchio's death was "the last straw" after a 15-year-old schoolboy in Rome killed himself in 2012, having allegedly been taunted as a homosexual on Facebook.

Facebook offers "report" links on its pages to allow the highlighting of offensive content, and in 2011 launched a "Stop Bullying, Speak Up" application to raise awareness of the problem. In Novara, a social media backlash against Miss Picchio's torment quickly emerged, with one online commentator, thought to be a schoolfriend, condemning the boys who videoed her.

She said: "Tomorrow I have to go back to school and see those idiots. I can't do it." Eight boys, aged 15 to 17, are being questioned by magistrates, including Miss Picchio's former boyfriend, who has reportedly claimed he was not at the party where she was filmed. In an interview with Italy's La Repubblica, the boy's mother described her son as "an extraordinary boy who has never given me problems". Italian magistrates have a record of challenging social media providers over offensive content. Three Google executives were given six-month suspended sentences in 2010 for allowing the posting of a film in Italy of the bullying of a handicapped student.

Prosecutors claimed that Google had allowed the student's privacy to be violated. The case was overturned on appeal last December, but a magistrate is now fighting that acquittal at Italy's Supreme Court.