A lawsuit filed in a U.S. District Court in Detroit alleges that automaker General Motors cheated on government diesel emissions tests.

According to reports, the lawsuit claims that GM pickup trucks with Duramax diesel engines include three devices that are rigged to allow more pollution on the road than during treadmill tests in the Environmental Protection Agency laboratory. The complaint on behalf of two truck owners against GM alleges that the devices were installed on diesel engines in the Chevrolet Silverado and GMC Sierra heavy-duty pickups, according to a Fox News report.

"These claims are baseless and we will vigorously defend ourselves,” GM said in a statement. “The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all U.S. EPA and CARB emissions regulations."

Diesel engines have been under scrutiny since Volkswagen made national headlines for a diesel emissions cheating scandal that has resulted in a nearly $15-billion settlement with the U.S. government.

The settlement has been shaped to offset the smog-forming NOx emissions from the 2L diesel vehicles sold by VW during the 2009 to 2015 timeframe. Emissions from the cars were found to be as much as 40 times above legal limits, contributing to unhealthful air.

And earlier this week, German officials from the Stuttgart public prosecutor’s office searched the premises of Daimler AG at several locations in Germany as part of an investigation into the possible manipulation of exhaust-gas after treatment in passenger cars with diesel engines.

According to reports, several federal and state authorities in Europe and the United States were investigating the emissions control systems used in Mercedes-Benz vehicles. In a press release issued on May 23, the automaker said it is “fully cooperating with the authorities.”