The husband, aged 35, along with the 23 year-old wife who recently converted to Islam, were initially arrested on charges of condoning terrorism.
However, national counter-terrorist prosecutors were brought in last week after investigators found the homemade fake stomach.
According to a source, no explosives were found but an analysis of their computer found they had consulted bomb-making information and photos of jihadists.
The couple have not been charged yet.
Their arrest comes on the heels of a foiled jihadist plot last week near Orleans southwest of Paris by two men, who investigators say were planning to attack soldiers, police and representatives of the state.
Meanwhile, in Belgium, authorities have charged ninth person in connection with the November 13 terror attacks in Paris.
According to a spokesman of the prosecutor’s office, the suspect had telephoned Hasna Aitboulachen, the cousin of ringleader Abdelhamid Abaaoud, several times after the attacks and before a police raid five days later in which they both died.
The man, identified as Abdoullah C. is a 30 year old Belgian national born in 1985. He was arrested on charges of terrorist murders and participation in the activities of a terrorist organisation.
The police are still looking for Salah Abdeslam, 26, who is believed to have fled from Paris to Brussels the day after the attacks.
– with AFP