An abandoned car filled with gas cylinders that was found parked near Paris' Notre Dame cathedral on Sunday may have been left at the landmark as part of a terror attack "test run," officials said Wednesday.

The car's owner, who is on a French intelligence service watch list of people suspected of religious radicalization, was in custody, Sky News reported. At least one other person had also been detained in the investigation.

"We think he may have been trying to carry out a test-run," a police official told AFP.

An employee of a nearby bar flagged the car Sunday morning as it was parked along the Seine River with its hazard lights flashing, according to two French officials.  

There were seven gas cylinders inside the car, with one empty cylinder in the front passenger seat and six others in the car's trunk, authorities said. No detonating device was present.

Documents with Arabic writing were found inside the car, the BBC reported.

French Interior Minister Bernard Cazeneuve said it still was not clear why the car was abandoned or what the intentions were of those under arrest.

Cazeneuve said there have been 260 arrests linked to extremist networks since the beginning of the year "and a significant number of these people were preparing attacks."

France is on alert after a deadly string of Islamic State attacks and threats against landmarks. News of the gas canisters' near Notre Dame broke hours before the release of a government-commissioned report on how the attacks have impacted France's lucrative tourism industry.

Algeria-linked extremists used gas canisters filled with nails during attacks on Paris in the 1990s.

The Associated Press contributed to this report.