French police have arrested more than 30 people in raids on housing estates near Paris, targeting the suspected ringleaders of riots last November.
Some 1,000 police took part in the pre-dawn sweep in and around Villiers-le-Bel, some 20km (12 miles) north of the capital, officials said.
The 2007 riots began in Paris's mainly immigrant suburbs after two teenagers died in a crash with a police car.
More than 100 policemen were injured at the time, some seriously.
In December, police handed out leaflets in the suburb calling for witnesses and promising rewards of up to several thousand euros for information.
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The clashes were a bitter reminder of the nationwide riots of 2005, when France was forced to call a state of emergency after weeks of violence in its poor and mainly immigrant suburbs.
Earlier this month, President Nicolas Sarkozy announced a three-year plan to deploy 4,000 more police and roll out a half-billion euro (£375m) aid lifeline to flashpoint neighbourhoods.
Mr Sarkozy also promised to help 100,000 people find work and declared a "war without mercy" on drug dealers.
