Police are to look into whether a suspected serial killer could be behind the unsolved Alps murders in which a British man, his wife and mother-in-law were killed in a forest car park.
Saad al-Hilli, Iqbal al-Hilli and her mother Suhaila al-Allaf were shot dead on holiday in Chevaline, near Annecy, in September 2012, along with a passing French cyclist, Sylvain Mollier.
Despite a massive manhunt, the investigation has all-but petered out.
Police are now questioning a 34-year-old ex-soldier who is the main suspect in two other cases in the area.
One relates to the disappearance of a 9-year-old girl in August at a wedding where the suspect was a guest, the other to the killing of a hitchhiking soldier in April.
The suspect, Nordahl Lelandais, has been in custody since September as part of the investigation over the disappearance of nine-year-old Maëlys de Araujo in the Chambéry region of south-eastern France.
He has been charged with kidnapping the girl, which he has denied.
"We are going to look at all the disturbing disappearances which have taken place in this region," Chambéry Prosecutor Thierry Dran told reporters.
When asked about the Alps murders, Mr Dran told Le Parisien: "Given this new development, we will be verifying (any connections), and that will naturally be done, to rule out or include (the suspect in the investigation). It would be wrong not to."
Annecy prosecutor Véronique Dénizot confirmed to the Telegraph that the case will be re-opened to probe Lelandais' possible involvement.
"Verifications will be made in due course" to establish if Lelandais has any links with the al-Hilli murders. His possible links will be examined "within a reasonable timeframe" when staff is available to do so, she said.
"There is no particular urgency but verifications will be made."
No motive has been found by police despite exhaustive investigations in Britain, France and Iraq. Investigators have previously suggested the murderer's profile could be military.
Other potential cases that may be linked to Lelandais involve Adrien Mourial, a 24-year-old Belgian citizen who went missing near Lake Annecy in July, and Jean-Christophe Morin and Ahmed Hamad, who vanished in 2011 and 2012 respectively.
The cases of 24-year-old missing soldier Arthur Noyer and the disappeared girl have gripped France and returned to the media fore this week.
Lelandais has denied all charges against him, either replying calmly to questions while in custody or simply refusing to respond to allegations put to him by investigators.
The skull of the missing soldier was discovered by a hiker in early September, while Maelys' body has not been found despite intensive efforts by hundreds of police, backed by dogs and helicopters, as well as volunteers.
She went missing at around 3am at a wedding in August where Lelandais was a guest of the groom.
The suspect is an unmarried dog lover with no long-term job who drove a black Audi which has emerged as a crucial piece of evidence allegedly tying him to both murder cases. Her DNA was found in the car, which he washed the following day.
The former military man, who has short cropped brown hair, lived with his parents in the village of Domessin and was found by investigators to be a frequent watcher of online pornography.
Analysing his internet searches, investigators also found that the martial arts fan had looked up "decomposition of a human body" after the disappearance of the soldier.
His lawyer, Alain Jakubowicz, has blasted police and prosecutors investigating the Maelys case for leaking damaging information against his client, while Lelandais' mother has also leapt to his defence.
"He did a few stupid things when he was younger but he's not a delinquent, he's a nice young man. He's not someone who's aggressive, you can ask the neighbours," she told the LCI news channel in September.
The French army has refused to comment to AFP about allegations in the media that he was discharged in 2005 after four years of service because of psychological problems and drug use.
The Paris Match magazine reported that he was convicted for arson in 2009.