Authorities in Italy have launched an investigation after a child, the only survivor of a deadly cable car crash in May, was taken to Israel by his grandfather.

Eitan Biran’s parents, younger brother and two of his great grandparents were among 14 people killed in the accident. The six-year-old had been staying with a paternal aunt in Italy since being released from hospital.

However, Eitan’s maternal relatives in Israel had sought custody.

Eitan’s family had lived in Italy for several years before the crash, and his paternal aunt Aya Biran-Nirko was granted custody in June.

On Saturday, however, Eitan was taken out by his maternal grandfather, Shmulik Peleg, who moved to Italy after the crash and had visitation rights.

He then took Eitan out of the country on a private jet, using the child’s Israeli passport. Israeli diplomats have since confirmed his arrival in the country.

Italy’s Corriere della Sera newspaper reported that Mr Peleg drove the boy to Lugano, Switzerland where they boarded the jet to Tel Aviv. Mr Peleg made the decision because he believed the boy was in poor “mental and physical condition”, the newspaper said.

Eitan’s maternal aunt Gali Peleg filed for adoption in August, claiming that the boy was being held hostage in Italy.

“We did not kidnap Eitan… we brought him home,” she told Israel’s Radio 103FM on Sunday, and claimed that Eitan’s parents had wanted to return to Israel prior to the crash.

The child’s paternal aunt, however, described the news as “another tragedy for Eitan”, according to Corriere della Sera.

Italian media report that prosecutors have opened a kidnapping investigation. An investigation into the cause of the crash in northern Italy is still under way, but prosecutors believe the car’s emergency brakes had been intentionally disabled.

When the main cable holding the car snapped, there was nothing to stop it reversing at over 100km/h (62mph) on a support cable, passing a support pylon and then plummeting to the ground and rolling down the mountain.

Thirteen people died at the scene, including a two-year-old child, while another child died later in hospital.

A number of people from the company that operated the cable car are currently under investigation over the incident. A technician has admitted installing a fork-shaped bracket to deactivate the emergency brake, which had reportedly been malfunctioning, earlier this year.

However, a cable car expert has alleged that earlier videos he took suggest the emergency brake was already disabled in 2014.