French authorities have ordered an internal police inquiry into the deaths of two teenagers whose motorbike collided with a police car.
A French state prosecutor has ordered the deaths to be investigated for manslaughter and non-assistance to persons in danger".
The deaths sparked rioting by youths in the northern Paris suburbs of Villiers-le-Bel and Arnouville.
Police said 21 officers were injured in the six hours of violence.
French President Nicolas Sarkozy, on a visit to China, urged calm.
"I want everyone to calm down and let the justice system decide who was responsible," he said in Beijing.
The violence was reminiscent of riots in 2005 that followed the deaths of two youths in the nearby suburb of Clichy-sous-Bois when Mr Sarkozy was interior minister.
A state prosecutor has ordered the National Police General Inspectorate (IGPN) to carry out a detailed inquiry into 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 the policeman driving the car from any responsibility for the incident.
Witnesses accused the police of leaving the collision scene
"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.
Following the Sunday evening collision, youths in the area went on a rampage, damaging shops and setting cars on fire.
Villiers-le-Bel police station was set ablaze and another in Arnouville was pillaged, police say. At least seven people were arrested.
French media reported two petrol stations were also torched and the Arnouville-Villiers-le-Bel railway station was damaged.
Riot police were sent to the area, but youths blocked their way with burning cars.
Police sources said the two teenagers 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.
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.