PARIS—Shares of French carmaker Renault plunged over 10% on Thursday as environmental officials revealed its diesel engines exceed emissions limits, although unlike the VW scandal, no cheating software had been found in the cars.

France's Environment Minister Segolene Royal made the announcement after a commission she appointed submitted test results of French and foreign vehicles. The tests found carbon dioxide and nitrogen dioxide emissions in Renault cars to be too high, as were those of several non-French automakers that were not identified.

Renault's stock closed down 10.28% at 77.75 euros after sinking by as much as 20% throughout the trading day in Paris after unions first reported that anti-fraud detectives had raided sites of the carmaker possibly in connection with the emissions probe.

"The news triggered a massive selling movement, it's a disaster that's pulling everybody down," said one Paris-based analyst, referring to falling auto stocks across Europe.

Suspicions of possible foul play raised fears that an ongoing Volkswagen pollution scandal was spreading to neighboring France. The German carmarker has admitted that 11 million of its diesel engine vehicles worldwide were fitted with pollution cheating devices.

But no such devices were found on the Renault vehicles and French Economy Minister Emmanuel Macron, on a visit to Berlin was quick to note that Renault was "not in any way a comparable situation" to that of troubled VW.

Both Macron and Royal expressed confidence in the French carmaker, in which the state holds a 19.7% stake.