French police are seeking a young woman after a car carrying seven gas cylinders was discovered near Notre-Dame cathedral in Paris.
A couple, aged 34 and 29, were also arrested on a motorway on Tuesday in southern France in connection with the incident and remain in custody, one official said.
The car owner was taken into custody but was later released because he had gone to police on Sunday to report that his daughter had disappeared with his car, a second official said.
His daughter, now sought by police, is 19 years old and was known to police for having the intention of leaving for Syria, officials said.
The Peugeot 607, which had no registration plates, contained seven gas cylinders, one of them empty, on the front passenger seat, police said.
It was found with its hazard lights flashing as if to attract attention, they said.
Interior Minister Bernard Cazeneuve said he was waiting for a report from investigators on what the possible motives were for the incident.
There was no detonating device present in the car, found on a Seine riverside stretch called the Quai de Montebello, metres from the Notre-Dame cathedral, one of Paris's many popular tourist attractions.
Documents with writing in Arabic were also found in the car.
More than 200 people have been killed in attacks by militant Islamists in France over the past 18 months.
France remains on maximum alert after calls by the Islamic State group for followers to attack the country, which is bombing the militant group's bases in Iraq and Syria.