The Peugeot 607 was discovered abandoned at the weekend with its hazard lights flashing, the sources said.
The owner of the car and another person, who are both known to security services, were arrested yesterday and anti- terror investigators have launched a probe.
France remains on high alert for terror attacks. In November, suicide bombers and gunmen killed 130 people in Paris in a series of attacks claimed by the Islamic State jihadist group.
That cylinder was found to be empty but five full cylinders were found in the boot of the car.
No detonators were found, police said.
The car was parked in a side street opposite the cathedral on the left bank of the Seine.
The car's owner was identified yesterday.
Notre Dame, a Gothic cathedral famous for its flying buttresses, stained glass windows and gargoyles, is one of Paris's most popular landmarks, attracting 13 million visitors each year.
Such attacks would create large numbers of victims without sacrificing suicide bombers, he told a parliamentary committee.
In July, 86 people were killed and dozens injured when a truck ploughed into a Bastille Day crowd in the Mediterranean resort of Nice. IS said the driver, Mohamed Lahouaiej Bouhlel, was one of its followers.
Less than two weeks later, two young jihadists murdered a priest near the northern city of Rouen.
France's top prosecutor said last week around 700 French nationals were currently in Syria.
Disclaimer: No Business Standard Journalist was involved in creation of this content
