Four French restaurant executives have been arrested on suspicion of illegally serving up British beef.

Shares in the Buffalo Grill chain of restaurants crashed by more than 90% on the news, before being suspended altogether.

It was illegal to import any beef from Britain between 1996 and 2002 because of the threat of BSE, or so-called mad cow disease.

The police investigation centres on the possible cause of four deaths in France from the fatal form of the disease that is passed onto humans by eating beef.

Two of the four people are believed to have dined in the Buffalo Grill before developing the disease.

Expansion plans

A spokesman for the firm denied the restaurant had been selling any British beef.

The firm's chairman and chief executive, Christian Picart, is amongst those arrested.

Buffalo Grill has a total of 260 outlets, having opened 26 new restaurants this year.

Its profits have been rising rapidly as part of its successful expansion drive into Switzerland, Belgium and Spain.

It was hoping to double the number of its restaurants again within the next 10 years.