TRENTON, Ont.

Volkswagen Canada ordered its dealers on Monday to stop selling diesel vehicles in Canada following revelations that the automaker rigged emission tests for about 500,000 of its models in Canada and the U.S.

“Volkswagen Canada has issued a stop-sale order to our deals for all of the affected vehicles pending resolution of this matter,” company spokesman Thomas Tetzlaff wrote in an email to the Canadian Broadcasting Company (CBC).

The move comes after the German government urged the carmaker to co-operate fully with U.S. authorities over news it manipulated emissions tests.

News of the scandal, along with the possibility of up to $18 billion in fines according to the U.S. Environmental Protection Agency (EPA), sent VW shares plunging 20 percent.

The EPA and the California Air Resources Board claimed to have found software in 482,000 cars that detects when a vehicle is about to undergo an emissions test and activates emission controls. Under normal driving conditions, the controls are dormant, releasing pollutants.

“I personally am deeply sorry that we have broken the trust of our customers and the public,” Volkswagen CEO Martin Winterkorn said in a statement.

The affected models date back as far as 2009.

In Canada, the diesel vehicles affected include the VW Jetta (2009-15); VW Golf (2010-15); VW Beetle (2013-15); VW Passat (2012-15); VW Golf Wagon/Sportwagon (2009-15).

Environment Canada told the CBC it works with the EPA on emissions verification, noting its emission standards are aligned with those in the U.S.

Environment Canada and the EPA took pains to stress that the pollution controls are not a safety issue and the cars remain legal to drive. But the EPA said the vehicles are a threat to public health.

The damage to the brand – VW marketed its diesel-powered cars as being better for the environment – is huge, as is the potential fine.

“The company will have to recall nearly 500,000 affected cars, which will cost it millions of dollars, and that’s even before the damage to its brand and potential fines,” Michael Hewson, chief market analyst at CMC Markets told the CBC.