The pair was picked up near Montargis, about 110 kilometres south of Paris.
Their detention raises to four the number of people held in connection with the suspect car, an abandoned Peugeot 607 which was parked several hundred metres from Notre Dame cathedral in Paris.
The first couple, who were detained at a service station on a road in southern France, were known to the security services for having links to radical Islamists.
Anti-terror investigators are probing the incident which comes as France is on high alert following a string of jihadist attacks, including last November's coordinated Islamic State (IS) group assaults in Paris by gunmen and suicide bombers who killed 130 people.
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