General view of the Volkswagen power plant in Wolfsburg, Germany Sept 22, 2015. [Photo/Agencies]

WASHINGTON - Volkswagen has admitted there are more diesel vehicles that use defeat devices to circumvent emissions tests, the US government said Friday.

Volkswagen officials told the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) on Thursday that they installed defeat devices in all Volkswagen and Audi vehicles equipped with 3.0 liter diesel engines for model years 2009 through 2016, the EPA and CARB said in a statement.

"Based on this information, EPA and CARB will continue to investigate and take all appropriate action under their respective authorities," the statement said.

On Sept 18, the EPA and CARB issued a notice of violation alleging that about 482,000 Volkswagen and Audi diesel cars equipped with 2.0 liter engines for model years 2009 through 2015 included defeat devices that circumvents EPA emissions standards for nitrogen oxides.

On Nov 2, the US regulators issued a second notice of violation alleging that Volkswagen installed defeat devices in certain Volkswagen, Audi and Porsche light duty diesel vehicles equipped with 3.0 liter engines for model years 2014 through 2016 that increase emissions of nitrogen oxide up to nine times EPA's standard.