The unidentified woman was apprehended in the eastern Paris suburb of Saint-Mande yesterday after a public appeal for her whereabouts following the November 20 discovery of the body of the girl on a beach in northern France.
The 36-year-old suspect is refusing to talk to police, but DNA tests are under way to identify her, regional assistant prosecutor Nathalie Bagny told AFP.
Surveillance video images had shown the woman and the child taking a train from Paris to the coastal town of Berck-sur-Mer on November 19, then the woman returning alone the next day, some hours after the girl's body was discovered.