At least four people have been arrested after riots in the northern French town of Amiens on Sunday.
The four are being questioned over arson, robbery and trafficking stolen goods.
Two nights of unrest left 17 police officers hurt, some by shotgun pellets. Rioting youths torched dozens of cars, a sports centre and a nursery school.
The violence is believed to have been sparked by a police spot check on the sidelines of a memorial for a young local man who died in a road accident. Some residents blamed heavy handed policing for the disturbance.