Annecy prosecutor Eric Maillaud said the man, from the Haute-Savoie region, was detained following the release in November of an identikit image of a mysterious motorcyclist seen near where the quadruple murder took place.
“This arrest, which may not be the only one, was the result of witness statements” that came in after the image was released, Maillaud said.
He said there was no apparent “direct link” between the man and the victims and sources expressed caution, saying the arrest may only be for questioning.
A source said police carried out a search of the man’s home near the scene of the crime, in the presence of his girlfriend. The source described him as a “taciturn mountain man” and a gun enthusiast who lives on the fringes of society. Maillaud said the man bore a “strong resemblance” to the man in the identikit image.
It is the first time anyone has been arrested in France in connection with the case, which has stumped investigators despite major efforts on both sides of the English Channel.
Saad al-Hilli, a 50-year-old Iraqi-born British tourist, was gunned down in September 2012 along with his 47-year-old wife Iqbal and her 74-year-old mother in a woodland car park close to the village of Chevaline in the hills above Lake Annecy.
Each was shot multiple times in their car and more than two dozen spent bullet casings were found near the vehicle.
The couple’s two daughters, aged seven and four at the time, survived the gruesome attack, but the older girl was shot and badly beaten.
The younger girl survived unscathed after hiding under her mother’s skirt for hours after the killings, initially escaping the notice of police.
A 45-year-old French cyclist, Sylvain Mollier, was also killed after apparently stumbling on the scene.
The family, which visited France numerous times, had been staying at the three-star Le Solitaire du Lac site.
Saad al-Hilli’s brother Zaid was arrested in Britain in June last year on suspicion of conspiracy to commit murder but police said last month there was insufficient evidence to press charges.
Investigators had looked at an inheritance row between the brothers but yesterday’s arrest focused attention on the possibility of a local killer. Police in the family’s home town of Claygate in Surrey said the arrest was not linked with UK efforts.
“The arrest has resulted from a line of inquiry in France and is not as a result of the investigation carried out in the UK,” Surrey police said.
The source close to the case said the arrest was “an important step forward in the investigation” but added that “other arrests should follow”. The source was cautious about the arrest, noting the lack of any links to the victims.