Police are bracing for violence in the southeastern French town of Firminy tonight after the death in custody of a 21-year-old Arab man sparked two nights of arson and car-burning.

The family of Mohamed Benmouna joined the authorities in calling for calm as youths from immigrant housing estates vented their disbelief of the official report that he had committed suicide.

The scene at Firminy, near the city of St Etienne, was calmer today after a post-mortem examination found that Mr Benmouna, who had been arrested on extortion charges, had hanged himself from the plasterboard wall of the cell and that there was no trace of other violence.

On Tuesday night, when Benmouna was in a coma, youths set fire to a community centre and a dozen cars. After he died on yesterday, they burnt another eight cars.

Mediators were sent to calm tempers in order to avoid a spread of violence of the type that erupted after the deaths of two teenagers in a Paris ethnic suburb in October 2005. The rampage spread across the country and thousands of cars were burned as youths from immigrant families fought police.

The last serious episode, in November 2007, was in response to the death of two boys in a collision with a police car in the northern Paris suburb of Villiers-le-Bel.On average, more than 100 cars are set alight by youths every night in French towns and suburbs.

France has been criticised by international organisations for the high rate of suicides in its overcrowded prisons and police cells. So far this year, 77 prisoners have killed themselves.

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president