A bomb disposal squad spent more than two hours at the Surrey home of the French Alps shooting spree victims today after police raised concerns about items found at the property.
Neighbours were evacuated from the area as experts examined the mock-Tudor house in the affluent village of Claygate.
Officers from the Royal Logistic Corps arrived in a bomb disposal truck at around 10am and left shortly after midday.
A cordon which had been extended to block the road in front of the property was later taken down.
Attention on the family home intensified as police in Annecy, France, waited to question seven-year-old Zainab al-Hilli, who has regained consciousness following the attack that left her parents dead.
Her father Saad al-Hilli, 50, was murdered in his car alongside his dentist wife Iqbal on Wednesday while the family holidayed in the picturesque region.
Mrs al-Hilli’s mother also died in the shooting along with Sylvain Mollier, 45, a French cyclist who apparently stumbled across the attack.
Zainab’s younger sister Zeena, four, who survived after she hid behind her mother, flew back to Britain with carers yesterday.
British police are now working alongside their French counterparts to unravel the mystery surrounding the four deaths.
Officers first entered the al-Hillis’ home on Saturday after a team of four French investigators, led by Colonel Marc de Tarle, arrived in the UK.
Police are looking at all aspects of Mr al-Hilli’s life to try to find a motive for the murders.
Investigators have disclosed that his brother, Zaid Hilli, approached UK police to deny any feud with his sibling over an inheritance.
It is believed detectives are also looking into Mr al-Hilli’s professional life for possible clues. The father-of-two worked as a contractor for a satellite technology company in Surrey.
Today’s search of his property appeared to focus on a shed or workshop at the bottom of his garden.
It came after police announced they had “concerns around items found at the address” and prompted speculation that officers may have found some kind of improvised explosive device (IED).
It is as yet unclear whether they unearthed anything of this kind.
Major Chris Hunter, a retired British Army counter-terrorist bomb disposal operator, said: “I imagine the police have discovered something they are unhappy with, something that is a potential improvised explosive device or an improvised explosive itself.
“It could be a hazardous, dangerous or unstable substance.”
The fact they only raised concerns two days after going into the house was perhaps because police investigating the shooting would have been looking for a “very different sort of evidence” or whatever they unearthed could have been “secreted or hidden somewhere”, he said.
Meanwhile, French police are waiting to speak to Zainab, who was shot and beaten during the ordeal and is seen as a key witness.
She remains under sedation after coming out of a medically-induced coma.
Public prosecutor Eric Maillaud said the child will be interviewed as soon as doctors allow it.
Her sister returned to the UK after two relatives – reportedly an aunt and uncle – travelled to France over the weekend alongside a British social worker and family liaison officers from Surrey Police.
The youngster is now under the care of the authorities and the social services, but Mr Maillaud revealed he did not know where she was going to stay.
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 found 25 spent bullet cartridges at the scene – a car park in the Combe d’Ire forest near Chevaline – while two mobile phones found in the al-Hilli’s bullet-ridden BMW are being analysed by police.
Each of the four victims of the atrocity was shot twice in the head.
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.
One man, thought to be one of the last people to see the family alive, told reporters the family had arrived at the isolated car park at least an hour before they were killed.
Laurent Fillion-Robin, 38, also said there was no sign of any vehicle following the family.
The builder said he was working on a house in Chevaline when he saw the red British-registered BMW drive past between 2.30pm and 3pm. The shooting was reported to police just before 4pm.
Mr Fillion-Robin added that he did not hear any shots fired that afternoon and said the car park, near Lake Annecy, was not the sort of place that families with young children would usually go.
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.
Mr Maillaud 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, a campsite in Saint-Jorioz they were staying at when the attack happened.