Days after a joint French-Cambodian investigation ruled out suicide in the mysterious death of Frenchman Laurent Vallier and his four children, a judge said investigators believed they had their first suspect.

Chem Rithy, an investigating judge with the Kampong Speu Provincial Court, said that investigators had issued a summons to the brother-in-law of Vallier’s wife for questioning.

“We will question one man who is the brother-in-law of the wife, because he used to have arguments with Vallier before,” Rithy said.

“We do not accuse him, but we do more investigation because that man also used to use drugs before.”

On Friday, the French embassy announced a re-investigation of the death and overturned a preliminary conclusion issued last year ruling the case a murder-suicide.

The bodies of Vallier and his four children were discovered in a car submerged in a pond behind the family’s home in January 2012, four months after they had last been seen.

Rithy told the Post earlier this week that investigators suspected three to five people were involved in the murder.

Tith Chhoun, Vallier’s father-in-law, said he had no information regarding the questioning of his son-in-law nor any further information on the case.

To contact the reporter on this story: May Titthara at [email protected]