An anti-racism group said Wednesday it has filed a lawsuit to find out whether France's police intelligence unit violated the law by keeping tabs on gang leaders' ethnic origins.

Classifying people by their ethnicity is illegal in France, and French anti-racism group SOS Racisme filed suit Tuesday to investigate whether police intelligence unit Renseignements Generaux, or RG, had done so.

Police quickly responded, saying they had not violated the law, which forbids classification by race, ethnic origin or religion in the aim of upholding the French ideal of treating people as individuals.

SOS Racisme pointed to a report by leading French daily Le Monde in February that said the RG had listed 436 suspected gang leaders from troubled areas by ethnicity in a report in January 2005.

According to the newspaper report, 87 percent of those listed in the police file were French. More than two-thirds were of North African origin, and another 17 percent had roots elsewhere in Africa.

Violating the ethnic classification law is a misdemeanor that can bring penalties of up to five years in prison and fines of up to $385,000. Because of the type of legal filing under French law, the case automatically garners the appointment of an investigating judge to look into the allegations.

SOS Racisme said ultra-right groups and Internet sites had sought to capitalize on the 2005 police report, and demanded that an investigating judge identify those who wrote and authorized it.

In a statement from police headquarters in Paris, officials acknowledged that they had kept tallies on the ethnicity of suspects taken into custody, but said they never labeled any specific person in connection with a racial group.

The statement also recalled that police are required to submit such files to a national commission on information and freedom for authorization — part of France's efforts to protect people from racial profiling.

The 1978 law that governs the issue has roots in France's shame over its collaboration with the Nazis during World War II, when Jews were marked with yellow stars and sent to death camps.