A Renault security manager was put under investigation on suspicion of fraud yesterday, an official at the Paris prosecutor's office said, as a case of suspected industrial espionage at the carmaker continues to unravel.

Dominique Gevrey, taken into police custody on Friday and questioned over the weekend by France's DCRI domestic intelligence agency, was placed in detention as requested by the prosecutor.

Gevrey and a second security manager, Marc Tixador, were believed to be the only people who knew the identity of the person on whose information Renault based its spy probe, the carmaker's lawyer, Jean Reinhart, said this week.

Tixador and Renault's security head, who were also held for questioning over the weekend, were released earlier yesterday.

"No charges have been filed against them," a police source said.

Renault fired three executives and lodged a legal complaint in January over suspected spying at its electric vehicle program amid fears that information was leaked to a foreign power, but the carmaker has since admitted it may have been tricked.

Key to the espionage investigation has been a probe into the possible existence of bank accounts in Switzerland and Liechtenstein, the final results of which were expected around March 20.

The fired executives have all denied any wrongdoing and are taking legal action against Renault.

If no evidence of bank accounts is found, a board meeting could quickly be called, a source close to Renault told Reuters.

Chief Operating Officer Patrick Pelata hinted his own job may be at risk if the case proves unfounded when he said the company would accept all the consequences "up to the highest level of the company, that is to say up to myself."

French Finance Minister Christine Lagarde also said earlier this month that the carmaker, which is 15 percent state-owned, must face "all the consequences."