French police are investigating claims that a burger chain serving only halal meat in restaurants with a strong Muslim clientele is discriminating against other customers.
Prosecutors in Lille ordered the probe on Friday, a spokesman said, after the Socialist mayor of the nearby town of Roubaix sued the Quick chain for switching to Muslim dietary laws in eight of its 350 branches.
Quick -- a rival to global chains like McDonald's in parts of Europe -- offers turkey and halal beef instead of pork in those branches.
"Why should the people of Roubaix be forced to go to Lille or elsewhere to find bacon?" Franck Berton, the mayor's lawyer, told Reuters.
French restaurants are under no obligation to offer a range of products, and there are plenty of kosher and halal eateries catering to Europe's biggest Jewish and Muslim communities.
The halal market alone was estimated at 5.5 billion euros in a December 2009 survey, and is growing strongly.
However, Mayor Rene Vandierendonck and other politicians have accused Quick of "communalism" or violating the French principle of equality.
While Quick started the halal service in late November, the public furor only erupted this week after far-right leaders criticized the chain -- just before regional elections in March.
The row has also touched a nerve laid bare by months of state-sponsored discussions over banning Muslim face veils and strengthening French national identity.
The veil ban has won support from some Muslim feminists. The identity campaign, however, has been widely criticized as populist electioneering, with some associated events descending into brawls or rants against Muslims and immigrants.