Youths have damaged police stations, shops and cars in two Paris suburbs, following the deaths of two teenagers whose motorbike hit a police car.
A prosecutor has ordered an internal police inquiry into possible manslaughter and "non-assistance to persons in danger".
The violence - reminiscent of riots in 2005 - lasted for more than six hours.
In 2005, the deaths of two youths in nearby Clichy-sous-Bois led to France's worst civil unrest in more than 40 years.
On Sunday night Villiers-le-Bel police station was set ablaze and another in Arnouville was pillaged, police say. At least seven people were arrested.
Burning cars
Clashes broke out on Sunday night after two teenagers - aged 15 and 16 - were killed when the motorcycle they were driving collided with a police car.
Police sources said the two were riding a stolen mini-motorcycle, and that neither was wearing a helmet.
The police car was on a routine patrol and the teenagers were not being chased by police at the time of the accident, police said. The collision wrecked the front of the car and smashed the windscreen.
Witnesses have accused the police of leaving the scene and of preventing local people from trying to help the youngsters as they lay in the road.
The brother of one of the victims has called for the officers involved to be convicted.
After the accident, dozens of youths went on a rampage, setting the police station in Villiers-le-Bel on fire, ransacking the Arnouville police station and torching two petrol stations.
Riot police were sent to the area, but youths blocked their way with burning cars.
French media report that the rioters also damaged the Arnouville-Villiers-le-Bel railway station and nearby shops.
Police inquiry
Meanwhile, a state prosecutor ordered the National Police General Inspectorate (IGPN) to carry out a detailed inquiry on the circumstances in which the two teenagers - named only as Moushin, 15, and Larami, 16, lost their lives.
In a preliminary report, the IGPN excluded any responsibility of the policeman driving the car. "The driver did not see the motorcycle arrive and was surprised by the violence of the collision," the report says.
Two witnesses said the police car was driving at 40 - 50kph (25 - 30mph) and had no revolving lights or siren on.
Interior Minister Michele Alliot-Marie, speaking in Villiers-le-Bel, deplored the deaths and called for "responsibility from everyone", adding "of course the circumstances [of the accident] have to be totally clarified and this will be the job for the judiciary."
The mayor of Villers-le-Bel, Didier Vaillant, appealed for calm and said he would ensure there was "an impartial investigation, for full light to be shed" on the accident.
A brother of one of the dead teenagers, Omar Sehhouli, said the rioting "was not violence but an expression of rage".
In 2005, country-wide riots erupted after the electrocution of two teenagers from another Parisian suburb - Clichy-sous-Bois - in an electricity sub-station. They were reported to have been fleeing police at the time.
Relations between police and young people in many deprived areas have continued to be tense ever since.
