Regulators have discovered that more VW-Group cars were cheating emissions tests, Engadget reported.
The California Air Resources Board reportedly discovered software in Audi cars that hid their CO2 output under examination.
According to reports, the discovery was made four months ago, but neither the regulator nor the vehicle manufacturer disclosed it.
Audi’s offending software was apparently designed to recognise test conditions and reduce gearing ratios.
However, the California regulator turns the wheel during testing, which disabled the software.
Audi may have used the software until May 2016, several months after Volkswagen was ordered to begin recalling its cars for similar offences.