Shares in carmaker Renault suffered a meltdown on the Paris stock exchange on Thursday after unions reported raids by anti-fraud detectives on the company, possibly to investigate emissions foul play.

At around 1130 GMT, Renault shares were down more than 20 percent at 69.02 euros ($75), while rival carmaker Peugeot's stock also fell sharply, by seven percent to 13.70.

Earlier, unions reported that French anti-fraud detectives have raided several production sites of Renault, possibly to investigate emissions foul play.

"Agents from the (anti-fraud unit) DGCCRF intervened in various Renault sites last Thursday," the CGT Renault union said in a tract.

The probe targeted the sites' engine control units which suggests, the union said, that the raids "are linked to the consequences of the Volkswagen rigged-engines affair".

Detectives took several personal computers belonging to Renault managers, the unions said.