German carmaker Daimler has opened an internal investigation into the way it certifies diesel exhaust emissions in the US.

The Mercedes-Benz brand owner said it was conducting the probe at the request from the US Justice Department.

"Daimler is cooperating fully with the authorities," the carmaker said.

It comes just after Volkswagen agreed a deal with the US over its emissions scandal, in which it will offer compensation and buy back some cars.

Last year, US regulators discovered that VW cars were fitted with software that could distort emissions tests.

And just this week Japan's Mitsubishi Motors admitted rigging data on some of its models' fuel efficiency, while France's Peugeot has been raided by anti-fraud officials as part of ongoing investigations on pollutants in the car industry. But Peugeot says the pollutant emissions are compliant.

Daimler said it would "investigate possible indications of irregularities and of course take all necessary action".

Six months ago the US Environmental Protection Agency said it would review diesel vehicle emissions in light of the VW revelations.

In addition, US owners of Daimler's Mercedes-Benz BlueTEC diesels filed a class-action lawsuit claiming the cars are programmed in a way that lets them emit illegal levels of emissions, similar to diesels made by fellow German carmaker Volkswagen.

Daimler says the lawsuit's claims are without merit and that the Justice Department investigation is unrelated.

The company is due to report first quarter results on Friday. 

(BBC)