Germany’s regulators said they are testing diesel vehicles made by foreign brands to ensure compliance with the country's emission rules according to reports, after Volkswagen AG admitted on Tuesday to irregularities in carbon dioxide emissions data of its cars sold in Europe.

"We are currently carrying out strict checks on diesel vehicles from other manufacturers including foreign ones," Transport Minister Alexander Dobrindt told the Bild daily, a German newspaper, on Saturday. The minister also said that his ministry was working on a legislation to ensure Volkswagen was made liable for additional costs due to higher-than-claimed emissions from its cars.

Volkswagen revealed an internal investigation Tuesday, which showed CO2 emissions and fuel consumption levels were concealed during pollution checks using a special device fitted on the engines. The company estimates around 800,000 cars sold in Europe to be affected.

Under severe fire from lawmakers, regulators and customers alike, the German carmaker said it would foot the bill for extra costs incurred by drivers in places where taxes are linked to CO2 emissions. 

According to estimates, Volkswagen could face a bill as high as 35 billion euros ($38 billion) in fines, lawsuits and vehicle refits for the two scandals.

The German transport minister's announcement  followed a directive by the European Commission to all 28 member states Thursday, urging them to widen their investigations into potential breaches of vehicle emissions, according to Reuters.

The minister also said that the European Union was working to create car emissions tests that would emulate on-road driving practices in the future. "The tests will therefore become stricter and will more closely resemble the normal driving behavior in road traffic," he told the Bild daily.