Post mortems are due to be carried out today on the three members of a British-Iraqi family - and another man - who were shot dead in the French Alps yesterday.
Further ballistics evidence and DNA test results are also due today as investigating officers say they are still trying to establish a motive for the killings.
The prosecutor in charge of the case has described the deaths as an act of "extreme savagery".
Two young girls believed to be the daughters of two victims survived and are under police protection.
The four-year-old girl is thought to be in a very distressed state, while her older sister is seriously ill.
French President Francois Hollande has said authorities will "do our utmost to find the perpetrators".
Mr Hollande, making his third visit to the UK, joined British Prime Minister David Cameron in pledging to get to the bottom of the tragedy.
Mr Cameron described the deaths as "terrible", adding: "I have spoken to the British ambassador in France and consular staff are working very hard so that we do everything we can... and to find out what happened in this very tragic case.
"Obviously the faster we can get to the bottom of what happened, the better."
Three members of the same family were found with fatal head injuries after a gunman opened fire on them while they were travelling through the picturesque Haute-Savoie region near Lake Annecy in their BMW estate car.
The driver was named by French media as Saad al-Hilli, from Claygate, near Esher. Neighbours said they believed he was travelling with his wife, Iqbal, and his mother-in-law, all of whom died during the shootings, alongside a French cyclist, found at the scene.
Mr al-Hilli's daughters, named locally as Zainab, seven, and Zeena, four, were also believed to have been in the vehicle when the gunman struck. Zainab was found violently beaten and is in a coma, fighting for her life.
Zeena was found alive underneath the bodies of her family about eight hours after the massacre.
She was found "terrorised, motionless, in the midst of the bodies" after fellow campers at a nearby site told officers the family had two children, public prosecutor Eric Maillaud said.
One theory is that shots could have been fired during a bungled armed robbery, with the dead cyclist - named as Sylvain Mollier - being a witness to the crime.