French and British police have begun conducting further searches at the home of Saad al-Hilli and his wife as detectives investigating the Alps killings prepare to interview the couple's relatives.
Officers began a detailed search of the family's mock Tudor property yesterday as they seek to establish a motive for the murders that saw each of the four victims shot twice in the head.
Mr al-Hilli, 50, was killed in his car alongside his dentist wife, 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.
Two relatives of the orphans, who were not identified for "security reasons", have travelled to France alongside a British social worker.
They are expected to visit the girls in the coming days, although it is unclear when they will be able to see Zainab as she continues to be treated in hospital. Both youngsters are under police supervision.
Surrey Police also revealed they had sent family liaison officers out to the country.
Investigators from the force entered the al-Hillis' family home in Claygate, Surrey, yesterday after a team of four French officers, led by Colonel Marc de Tarle, arrived in the UK.
A tent was erected at the front of the address before scenes of crimes officers in full protective suits began combing through the family's belongings.
The caravan in which the family had been staying at the Le Solitaire du Lac campsite in Saint-Jorioz was also examined by police.
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.
Speaking about the French-led investigation yesterday, Assistant Chief Constable Rob Price from Surrey Police, said:
Investigators have disclosed that Mr al-Hilli's sibling approached UK police to deny any feud with his sibling over money.
French public prosecutor Eric Maillaud said the brother would be interviewed along with the rest of the al-Hilli family as witnesses as part of the investigation.
It is also believed detectives will look into Mr al-Hilli's profession, with reports emerging that he was working as a contractor for a satellites technology company in Surrey.
Four-year-old Zeena has spoken to police and confirmed that two of the victims were her parents, but said she did not know the Swedish woman very well.
Mr Maillaud said they were working with Swedish authorities as they try to confirm the woman's relationship to the family.
French authorities have also asked their Italian and Swiss counterparts to help them in their hunt for the killer or killers.
Witnesses have said they saw a green four-wheel-drive vehicle in the area at the time of the killings, and possibly a motorbike.
Investigators have found 25 spent bullet cartridges at the scene on the outskirts of a forest near Lake Annecy, while two mobile phones found in the al-Hilli's bullet-ridden BMW are being analysed by police.
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, Mr Maillaud said.
The prosecutor revealed the family had visited France a number of times before and it was not the first time they had been to Le Solitaire du Lac campsite.
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.
Some media reports have suggested that Mr al-Hilli, an engineer who left Saddam Hussein's Iraq several years ago, was known to the security services and was put under surveillance by Metropolitan Police Special Branch during the second Gulf war.
A Scotland Yard spokesman said they could not comment. But it is understood there is no link between the deaths and any national security issues.