Two young British girls who survived the horrific shooting of their family in France eight years ago will be re-interviewed to solve a mystery.

They were seven years old when Zaynab al-Hilli was there and his sister Jenna was four The Alps witnessed the murder of their parents, their grandparents and a passing cyclist.

The killer has not been identified and a number of theories have been investigated, but no motive has been identified for the September 2012 bloodbath on a mountain road near the picturesque town of Annecy.

Saad al-Hilli, 50, his wife Iqbal, 44, and his mother, Suhaila al-Allaf, 4, all died in the attack, where a lone gunman fired 25 shots at a parked car.

Zainab, now 15, and Jenna, 12, were cared for by other members of their family who were of Iraqi descent.

Ansir prosecutor Veronica Denizot said: “British judicial authorities have allowed two Al-Hili daughters to stand trial again.

“The older girl was originally heard when she came out of the hospital in Grenoble after the incidents and she gave investigators some details to the magistrates involved in this dossier.”

Zainab escaped by being shot in the shoulder and beaten around the head. He was seen stumbling on the side of the road.

Gina was discovered with a trunk under her dead mother’s feet in the back of the car.

Mrs Denizot said: “If kids can talk again, give new material, maybe they have something new to say that will help.

“So far they have been severely traumatized, and have been misjudged.”

Mrs Denizot said the “slightest new recollection” of one of the girls was likely to lead to a resumption of the suspended investigation.

“Perhaps a detail, a small element that could reopen the investigation. This is something we want to achieve with the help of the British authorities.”

The family was on a camping trip and their BMW was parked next to a wooden block when they were attacked for no apparent reason.

One theory was that Mr. Al-Hilli was attacked for working as an engineer, while concentrating on a single row to the will of the family, but no specific purpose was established. A local controversy was considered the most likely, and the family was easily and innocently caught up in it.