The probe came at the request of the US Department of Justice (DOJ) to look into the Daimler’s certification process for diesel exhaust emissions.
In the same breath, the company defended itself against a class-action lawsuit filed by legal firm Hagens Berman Sobol Shapiro in February, which suggested US Mercedes-Benz diesel vehicles are fitted with devices that can bypass emissions regulations.
Daimler lashed out, saying the action was “without merit”, adding that it will “defend itself against them with all available legal means”. It said it “is cooperating fully with the authorities” and will “investigate possible indications of irregularities and of course take all necessary actions”.
Shares in Daimler AG were down 5.69 per cent before noon Friday.
News of the investigation came a day after Volkswagen said it will draw from a $1bn (£697m) compensation fund to buy back or fix 500,000 diesel cars in the US that had devices to cheat emissions tests.
French anti-fraud investigators also raided the offices of PSA Peugeot Citroen on Thursday, amid ongoing vehicle pollutant investigations.
The company said there was a “seizure” of company documents by France's General Directorate for Competition Policy, Consumer Affairs and Fraud Control (DGCCRF). In January, tests of its vehicles led by French environment minister Ségolène Royal showed “the absence of anomalies”.
Mitsubishi also admitted on Wednesday that its employees had faked fuel economy data in tests of four different vehicles.
The falsified data concerns some 468,000 Nissan brand vehicles, parent company Mitsubishi said. The finding came after an internal investigation by the company of irregularities in Nissan data. Shares in Mitsubishi Motors were down -13.55 per cent early Friday.