Volkswagen designed software to meet clean-air standards during official emissions testing, but that turned off during normal operations, US and California regulators charged.
As a result, the diesel cars emit greater-than-allowed quantities of pollution linked to smog and various health ills.
A notice of violation posted Friday said the rigged software was used in five diesel models, including several of the company’s best-sellers. An EPA statement hinted of a future recall, saying it was “incumbent on Volkswagen to initiate the process” to fix the affected cars’ emissions systems.
Volkswagen had no comment about the allegations Friday.
The allegations prompted sharp criticism of Volkswagen from environmental and consumer protection groups.