Police in France have detained another couple in connection with a car loaded with six full gas canisters that was found near the Notre Dame cathedral in Paris Sunday.
Two other people with known links to radical Islamic groups had been arrested Tuesday in southern France.
The abandoned car with no license plates was reported to police by a bar employee who noticed a gas canister on the back seat when he walked past the vehicle Sunday.
Police detained the owner of the car – also known to authorities for ties to radical Islam – Tuesday but released him shortly after. The car owner’s daughter is still being sought by police for questioning.
Police searched the car and found no detonation mechanism for the canisters. Officers speculated that the car's flashing hazard lights may have been turned on to attract attention. "We think he may have been trying to carry out a test-run," one police official told AFP.
French authorities are on high alert for terror activities after two separate incidents allegedly perpetrated by the Islamic State group over the past year have left more than 200 people dead. In November, a coordinated attack in Paris killed 130 people, and a man driving a truck along a crowded boardwalk in Nice left 86 people dead.