A relative of a French family of four who have been missing since mid-February has admitted killing them, media reports say.
Pascal Troadec's former brother-in-law, named as Hubert C, reportedly told investigators he had killed them in a row about the inheritance of gold bars.
He is believed to have battered them to death with a blunt object at their home in Nantes, Le Parisien newspaper said.
His DNA is said to have been found at their home.
He was arrested along with Mr Troadec's sister, his ex-wife, in Brest. French media say items belonging to the family were found there.
Pascal and Brigitte, both aged around 50, their son Sebastien, 21, and daughter Charlotte, 18 were last seen on 16 February.
RTL reported that it is not yet known whether Hubert C has told police where he left their bodies.Image copyright AFP/Getty Image caption Pascal Troadec's sister and former brother-in-law are being questioned in Brest
Hubert C, 46, had already been interviewed by investigators at the beginning of their inquiry into the family's disappearance, but he told them he had not seen the Troadecs for several years, French media reported.
However his DNA was reportedly later found on a glass left in a sink in their home and also on Sebastien's car, which was found last Thursday in the port of St Nazaire.
A day earlier, a social security card and a pair of trousers belonging to Charlotte had been found by a jogger in a forested area near Brest.
In a search of the family's house last week, investigators found bloodstains matching the DNA of the parents and Sebastien, but not of the daughter.
Traces of blood were found on Sebastien's phone, on Brigitte's watch and under the stairs, and it appeared that someone had tried to wipe them away.
The role of Lydie Troadec - Hubert C's ex-wife and Pascal's sister - was not yet clear, reports said.Image copyright AFP Image caption Charlotte's belongings were found in a forested area