Flying Molotov cocktails and torched cars were seen in a troubled neighborhood outside Paris on Monday.
President Nicolas Sarkozy, visiting China, appealed for calm, while police braced for more problems. With more than 20 police officers injured and two police stations attacked in a first night of rioting Sunday, the violence was a reminder of the tensions that drove weeks of rioting in 2005 in poor neighborhoods with large minority populations.
Anger focused on police, with residents claiming that officers left the scene of Sunday's crash without helping the two teens whose motorbike collided with their car. Officials cast doubt on the claim but the internal police oversight agency was investigating nevertheless.
Investigators were still trying to piece together exactly what happened in the Sunday afternoon crash in Villiers-le-Bel, a town of public housing blocks home to a mix of Arab, black and white residents in the French capital's northern suburbs.
Police officials said the motorbike ignored traffic rules and crashed into the police vehicle, and that the bike was unregistered and thus not authorized for use on French roads. Neither of the teens - aged 15 and 16 - was wearing a helmet, and the prosecutor's office said the bike was going at maximum speed.
The internal police oversight agency opened an inquiry into whether the deaths were manslaughter and whether the officers failed to help the teens, a police official said, speaking on condition of anonymity because he was not authorized to speak to the media.
An alcohol test showed that neither of the officers had been drinking, and initial inquiries suggested they did not appear to have caused the crash, police said. The prosecutor, Marie-Therese de Givry, told LCI television that the officers called rescue services to the scene.
Villiers-le-Bel was on edge Monday for a second night, with cars burning and Molotov cocktails thrown in a neighborhood of housing projects.
"The situation is tense; there are a lot of police on the ground to prevent more flare-ups," said Gaelle James of the Synergie police officers' union.
In Sunday's violence, eight people were arrested and 21 police officers were injured - including the town's police chief, who was beaten in the face when he tried to negotiate with the rioters, police said.
Also Sunday, witnesses said, police fired rubber pellets at youths. Two police stations were targeted, one with Molotov cocktails. A McDonald's restaurant was burned, as were about 15 cars and several garbage cans.
Sarkozy said: "I want everyone to calm down and let the justice system determine who was responsible."
Residents drew parallels with the 2005 riots. That unrest was prompted by the deaths of two teens electrocuted in a power substation while hiding from police in a suburb northeast of Paris.
A recent study by the state auditor's office indicated that money poured into poor French suburbs in recent decades had done little to solve problems vividly exposed by the 2005 riots, including discrimination, unemployment and alienation from mainstream society.
The head of the opposition Socialist Party, Francois Hollande, called the latest violence the result of "a social and political crisis" and lamented the "climate of suspicion, of hate, that can exist in many neighborhoods."
"Promises were made. We want to see the results," Hollande said on France-Inter radio of government pledges to address suburban tensions. "How long have we been talking about a 'plan for the suburbs?"'