Sources on the French side of the team investigating the murders say it is a matter of asking questions of Zaid Al-Hilli on his feud with his brother, their father's inheritance and their father's money in Switzerland.
He is in custody as a result of moving from being a witness to a suspect. We are told they have no more elements of proof at this stage.
On Wednesday it was made very clear that Zaid Al-Hilli was not a suspect, although I was told "this could change at any time".
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The pair, including a man in his 50s, were struck around midday on the Pen y Fan mountain range in Powys, mid-Wales.