Annecy prosecutor, Eric Maillaud speaks during a news conference in Annecy, France
A police search operation has taken place at the Surrey home of a British man shot dead in the French Alps along with his wife and two others.
Three French officers, accompanied by Surrey Police, began examining the home of Saad al-Hilli, 50, in Claygate, reports the BBC.
They have also asked Italian and Swiss counterparts to help them in their hunt for those responsible.
Post-mortem tests showed all those killed were shot twice in the head, French prosecutor Eric Maillaud said.
Maillaud told a news conference at Annecy near to the site of Wednesday's killings that examinations were completed on Friday night, but refused to go into any more detail.
Meanwhile, speaking outside Surrey Police headquarters, Colonel Marc de Tarle, who heads the National Gendarmerie Criminal Affairs Bureau, said the investigation was likely to be "long and complex" and thanked the force for its support.
Two relatives have gone to France to comfort al-Hilli's daughters, who remain in hospital, and are under police protection.
The man and woman arrived in France on Friday night, accompanied by a British social worker and family-liaison officers from Surrey Police, and are expected to see four-year-old Zeena later.
Zeena spent eight hours hiding in the car before being found by officers.
Police said she was between her mother and the older woman, and hid under her mother's skirt when the shooting started.
Her sister, seven-year-old Zainab, remains in a medically-induced coma in Grenoble University Hospital after being shot and beaten.
The BBC's Imogen Foulkes, in Annecy, said: "Police say they hope a visit will take place soon, but add that any contact must be in the presence of French investigators - a reminder that the al-Hilli family itself is part of their inquiry."
Maillaud told reporters Zeena had been interviewed but he did not see a "need" to speak to her again as she "did not see anything" after taking shelter at her mother's feet.