PARIS (Reuters) - French and British police began searching the house on Saturday of a British man shot dead in the French Alps with his wife and another woman and a state prosecutor said the man's brother would be officially questioned as part of the investigations.

Forensics experts who performed autopsies on the three victims and a passing local cyclist who was also shot dead, determined all four had been shot twice directly in the head.

"The four people were killed by several bullets and ... were victims of shots straight to the head," State Prosecutor Eric Maillaud told reporters.

Maillaud confirmed the people killed in the car were a couple from Britain - on a camping holiday in the Annecy region with their two daughters - and an older woman.

The girls, aged seven and four, survived and are under police protection in hospital after the shootings on a remote forest road near the village of Chevaline on Wednesday.

Maillaud said a family feud over money was one of several motives being considered for the murders and the brother of Saad al-Hilli, the Iraqi-born British driver, would be formally questioned.

He said he understood the brother had denied any dispute with Hilli, who lived in Surrey, south of London.

"It's clear that during an investigation we will try and find out as much about the life of the Hilli family," Maillaud said.

The prosecutor said investigators had gleaned little from their "moving" chat on Friday with the four-year-old girl, who is in a psychiatric hospital in the city of Grenoble, accompanied by a nurse and British embassy staff.

He said members of the family had arrived on site, but declined to say who they were.

Police hope Hilli's seven-year-old daughter, who was still in an artificial coma in a Grenoble hospital after suffering serious skull fractures, will be able to eventually provide more information.

"The two girls are doing as well as can be expected," Maillaud said.

(Reporting by Johnny Cotton in Chevaline; Additional reporting and writing by John Irish; Editing by Sophie Hares)