The announcement comes on the same day that Germany’s transport minister said Volkswagen rigged emissions tests on some 2.8 million diesel vehicles in that country following revelations last week that they’d manipulated tests conducted by the U.S. Environmental Protection Agency.

“EPA may test or require testing on any vehicle at a designated location, using driving cycles and conditions that may reasonably be expected to be encountered in normal operation and use, for the purposes of investigating a potential defeat device”, EPA told automakers in the letter. And on Friday, the California Air Resources Board (CARB) sent other automakers a tersely worded letter saying it would now subject other cars to the same tests that found Volkswagen’s defeat devices.

VW’s software figured out when the cars were being tested in a laboratory and turned on pollution controls. With the controls off, the vehicle’s exhaust contained up to 40 times more pollutants than allowed by law. Its stock price tanked, its reputation has been damaged and its CEO resigned on Wednesday.

Joint investigations between EPA and CARB have “been very successful in protecting human health and the environment”, said Janet McCabe, the agency’s acting administrator in the Office of Air and Radiation.

A week ago the watchdog revealed that Volkswagen had used engine management software to detect when a motor was undergoing emissions testing, and temporarily change the engine output to pass the examination.

The scandal now engulfing VW, which has admitted to outfitting cars with software designed to give false readings on emission tests, is unique both for the number of vehicles involved, and the digital complexity.

In 1973, the EPA accused the vehicle manufacturer of installing defeat devices in cars it wanted to sell in the 1974 model year.

The agency also plans to redeploy some of its 23 mobile emissions testing platforms, the system that West Virginia University researchers used to discover the testing scam in the first place. But now all cars will face added inspection for emissions cheating.

Meanwhle Friday, with Volkswagen’s cheating on 482,000 cars in the American market thrusting her agency into the spotlight, McCarthy spent the morning consulting with an unlikely source.

VW has had to set aside €6.5 billion ($7.3 billion) to deal with the issue, but the final total could far exceed that.

“I don’t think it’s fair to say that this would never have been uncovered”, he says.