PARIS (AP) — French media say the former brother-in-law of a missing French couple has confessed to killing them and their two adult children.

Citing the Nantes prosecutor, Ouest-France newspaper said Monday that the brother-in-law was detained Sunday. The newspaper and RTL radio said a dispute over an inheritance is at the heart of the investigation into the missing Troadec family.

Traces of blood from the parents, Pascal and Brigitte, and from son Sebastien, were found on the staircase and ground floor during an initial search Feb. 23 in the parents' home in Orvault, a suburb of Nantes. The national health card of their 18-year-old daughter, Charlotte, was found in a pair of trousers in a ditch more than 270 kilometers (170 miles) away.

The family phones have gone unused since Feb. 17.