ANNECY, France: French police are investigating whether a money feud between brothers may have been at the heart of a shooting that killed three members of a British-Iraqi family in the French Alps, prosecutors said Friday.

"It seems that there was a dispute between the two brothers about money. This seems to be credible information coming from the British police," prosecutor Eric Maillaud told AFP.

"The brother will have to be questioned at length. Every lead will be meticulously followed."

He warned against drawing early conclusions however, saying it was difficult to imagine how a family feud could "pass from a financial dispute to a quadruple murder".

A French police source said the brother of victim Saad al-Hilli, a 50-year-old Briton born in Iraq, had presented himself to British police on Thursday to proclaim his innocence and cooperate in the probe.

Hilli, his wife and mother-in-law are believed to have been killed in the shooting Wednesday in a forest parking lot in a French Alpine tourist area, along with a local cyclist.

All four were shot in the head, prosecutors said, in a killing that bore many of the hallmarks of a professional assassination.

Two young girls believed to be the daughters of the victims survived, including a four-year-old who hid beneath her dead mother's skirt for eight hours and at first went undetected by police. Her seven-year-old sister was seriously injured.

Autopsies were due to be conducted on the bodies Friday and DNA tests carried out so authorities in France could formally confirm the identities of the victims.

Neighbours in England said Hilli was an engineer and identified the other victims as his wife Iqbal, who was carrying an Iraqi passport, and his mother-in-law, who had a Swedish passport. The couple's daughters were named as Zainab, aged seven, and Zeena, aged four.

Authorities in France identified the fourth victim, a cyclist who apparently stumbled across the scene by chance, as Sylvain Mollier, a father of three who lived in the area and worked in the nuclear industry.