Caouissin was let out of custody on Wednesday to show investigators where he had hidden the body parts on his farm in western France, according to Nantes prosecutor Pierre Sennès. Search teams and sniffer dogs have been scouring the grounds.
The 46-year-old has said he used a crowbar to kill his brother-in-law Pascal Troadec and his wife Brigitte, both 49, along with their two children Sébastien, 21, and Charlotte, 18.
After killing them, he dismembered the bodies. He then burned some of the body parts and buried others.
The family of four had been missing for nearly two weeks before Caouissin was arrested, along with his wife Lydie Troadec – Brigitte’s sister – on Sunday.
He was charged and jailed on Monday. His wife has also been charged with helping dispose of the bodies, and remains in custody in Nantes.
Sennès said during a press conference on Monday that Caouissin murdered the Troadecs in their home on 16 February.
The former shipyard employee told investigators that he thought Pascal Troadec had unjustly kept valuable gold coins for himself, when the coins should have been shared with him.
The gold coins were supposedly part of an inheritance.
Sennès said during a press conference on Monday that Caouissin had long harboured “great rancour” over the inheritance dispute.
However the existence of these coins, as well as their value, have yet to be confirmed.