[3] La Mansonnière cave was discovered by the Speleo Club du Rond Point de L'Aigle (SCRPLA) in 1977.
The Cave was originally called "La Grotte de Bellou sur Huisne", after the name of the local commune in southeastern Orne county, Normandy.
The entrances were walled up, but permission was obtained to gain entry to the labyrinth, referred to by the mushroom workers as 'clay pockets'.
French cavers later renamed the cave and engaged in extensive digging, removing much of the valuable varve deposits which the SCRPLA had hoped to preserve for study by professional soil scientists.
However, they have located detailed descriptions of at least one cave explored by the Parisian water authorities in the nineteenth century.