Investigators are hoping the seven-year-old British girl who survived the shooting of three members of her family will provide the key to solving the killings.
Iraqi-born Saad al-Hilli, 50, was gunned down in his car alongside his dentist wife, named by neighbours as Iqbal, and a woman believed to be her mother.
The couple’s children, four-year-old Zeena and Zainab, seven, are apparently the only witnesses to the shootings on an isolated French Alpine road and are now under police protection.
Investigators are waiting for the green light from medical staff at Grenoble University Hospital to talk to Zainab as the motive behind the killings remained a mystery.
Annecy prosecutor Eric Maillaud said detectives hope the youngster, who is in a stable condition, will recover sufficiently from the trauma to speak to them and that her memory was not damaged.
“We are waiting for the ballistic team’s report and, when possible, a hearing with the eldest girl,” said Mr Maillaud.
“Maybe she can give us information on the number of people present for example, or the colour of their skin, and other elements of description that might allow us to consider a bit more seriously a first lead.
“Medical staff have not yet given us access to the girl. We are waiting for their decision.”
Zainab was beaten repeatedly around the head and shot in the shoulder in the attack on the Surrey family, which took place on Wednesday.
She was hit with “tremendous ferocity”, said the prosecutor.
Her younger sister was found alive in the BMW estate underneath the bodies of her relatives around eight hours after the massacre, which also saw a passing French cyclist, Sylvain Mollier, 45, shot dead.
Mr Maillaud said he did not expect the four-year-old to be able to help police.
“She is a little girl who was hidden. It’s not her who will help us progress the inquiry.”
Police have revealed there were signs of a vehicle braking at the scene but no weapon had been found and no arrests had been made.
It was also unclear if the shootings were carried out by one killer or a number of people.
One theory is that shots could have been fired during a bungled armed robbery, with Mr Mollier being a witness to the crime.
But speculation about other possible motives, including a pre-planned attack by professional hitmen, remained rife.
Mr Maillaud said British police had reported that the girls’ father was in a dispute with a family member concerning money.
He said: “It’s an important piece of information that we will investigate. But all other lines remain open.
“We are not ruling anything out – a deal gone wrong, the possibility that this family, like the French cyclist, were in the wrong place at the wrong time – at this stage we can’t rule anything out.
“At the moment we are gathering a number of plausible bits of information. Investigators are trying to give priority to the leads which seem the most serious, the most plausible.”