French and British police have begun a detailed search of the home of the couple gunned down in the Alps after it emerged all four people who died were shot twice in the head.
Saad al-Hilli, 50, was killed in his car alongside his dentist wife, named by neighbours as Iqbal, on Wednesday.
An older Swedish woman travelling in the car also died in the shooting, along with Sylvain Mollier, 45, a French cyclist who apparently stumbled across the attack in Chevaline.
The couple's four-year-old daughter Zeena lay undiscovered under her mother's corpse for eight hours after the murders, while her seven-year-old sister Zainab remains in a medically induced coma after being shot and beaten.
Post-mortem examinations revealed each of the victims killed in the attack had been shot a number of times, including two hits to the head, public prosecutor Eric Maillaud said.
Police entered the al-Hillis' family home in Claygate, Surrey, as a team of four French officers arrived in the UK. The caravan in which the family had been staying at the Le Solitaire du Lac campsite in Saint-Jorioz was also examined by police. French authorities have now asked their Italian and Swiss counterparts to help the investigation.
Surrey Police erected a tent at the front of the al-Hillis' home as they prepared to conduct a search of the property with the French police team, led by Colonel Marc de Tarle. Two French detectives entered the house with two British officers, followed by scenes of crimes officers in full protective suits.
Families have been visiting the home to leave floral tributes outside, along with teddy bears and a Mr Men 'Little Miss Trouble' book.
Two relatives of the al-Hilli family have travelled to France, alongside a British social worker, and will visit the girls who are under police supervision. However it was unclear when they would be able to see the elder girl, Zainab, as she continues to be treated in hospital.
Police plan to look at aspects of Mr al-Hilli's life to try to find a motive for the murders and also speak with his brother, named in reports as Zaid Hilli. Investigators said Mr al-Hilli's brother approached UK police to deny any feud with his sibling over money. Mr Mauillard said the brother would be interviewed along with the rest of the al-Hilli family.