The French plot was at the “advanced stage” of preparation and was discovered after a French national — described as being at a “high level” in the plot — was arrested this morning, Cazeneuve said.

There did not appear to be links “at this stage” between the plot foiled in France and the Paris or Brussels attacks, he added, saying the arrest is the result of weeks of investigation and the individual was involved in a “terror network” that planned to strike.

The raids in Argenteuil, about 8 miles outside of the center of Paris, were ongoing and the streets were sealed off.

Investigators are actively seeking a second suspect in the Brussels metro bombing who has been seen on surveillance camera footage inside the subway station with suicide bomber Khalid El-Bakraoui, a Belgian police source told ABC News.