French and British police will conduct further searches at the home of Saad al-Hilli and his wife today as detectives investigating the Alps killings prepare to interview the couple's relatives.

Officers began a detailed search of the family's 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, 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.

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.

Investigators from the force entered the al-Hillis' family home in Claygate, Surrey, yesterday after 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.