On Wednesday, the Paris prosecutor's office revealed that a criminal terrorist investigation was underway after a Peugeot 607 parked near Notre Dame Cathedral was found with seven gas canisters and pages written in Arabic.

ABC News reports that the prosecutor's office said that a 34-year-old man and a 29-year-old woman, whom the office said were “radicalized,” had been arrested on Tuesday. The couple was arrested near the southern town of Orange; prosecutors said French security services were aware of them for their alleged links with "radical Islamism.”

The car’s license plates had been removed and the warning lights were flashing. One police official told AFP, "We think he may have been trying to carry out a test-run.” No explosives or detonators were found in the car; one source close to the investigation told l'Express, "They were not linked to any kind of fuse.”

The owner of the car had alerted police that his radicalized daughter, who was not the woman arrested with the man, was missing but did not inform them that the car was gone. The man’s daughter is being pursued.

Two officials who wished to remain anonymous as the investigation is ongoing, said an employee of a bar near Notre Dame Cathedral alerted police about the car. French Interior Minister Bernard Cazeneuve said the intentions of the couple ere not clear as yet. He also said 260 arrests have been linked to extremist networks in 2016, and “a significant number of these people were preparing attacks."

Notre Dame is visited by roughly 13 million visitors every year.