The U.S. Environmental Protection Agency on Friday ordered Volkswagen to fix nearly 500,000 VW and Audi diesel cars that the agency said are intentionally violating clean air laws by using software that evades EPA emissions standards.

VW, which owns Audi, faces billions of dollars in fines, although exact amounts were not determined.

The cars, all built in the last seven years, include a device programmed to detect when they are undergoing official emissions testing, the EPA said, adding that the cars only turn on full emissions control systems during that testing. The controls are turned off during normal driving situations, the EPA said.

The EPA called the company's use of the device illegal and a threat to public health.

The EPA called on VW to fix the cars' emissions systems, but said car owners do not need to take any immediate action. The violations do not present a safety hazard and the cars remain legal to drive and sell, the EPA said.

The German automaker said in a statement it is co-operating with the investigation, but declined further comment.

VW faces possible $18B fine

The EPA said VW faces fines of up to $37,500 per vehicle for the violations — a total of more than $18 billion US. No final total was announced.

Despite the seriousness of the violation, the EPA said VW will be given "a reasonable amount of time to develop a plan to complete the repairs," including both the repair procedure and manufacture of any needed parts.

It could take up to a year to identify corrective actions, develop a recall plan and issue recall notices, the EPA said.

The allegations cover roughly 482,000 diesel passenger cars sold in the United States since 2008. Affected models include:

  • Jetta (Model Years 2009 - 2015)
  • Beetle (Model Years 2009 - 2015)
  • Audi A3 (Model Years 2009 - 2015)
  • Golf (Model Years 2009 - 2015)
  • Passat (Model Years 2014-2015)

It's not immediately clear if any VWs or Audis sold in Canada are facing the same issue. VW Canada said in an email to CBC News it first became aware of the EPA action Friday morning. It said it would "co-operate fully with Environment Canada to understand the implications for the Canadian market and what actions, if any, may be required in Canada."

Environment Canada said it was in talks with the EPA "to further examine this issue and assess potential implications for Canada."  

With files from CBC News