The American auto giant was fined after approximately 5.9 million vehicles were found to release more emissions than reported, a National Highway Traffic Safety Administration (NHTSA) spokesperson told AFP.

The vehicles in question, with model years between 2012 and 2018, showed more than 10% higher carbon dioxide emissions in tests, on average, than what GM reported, according to the Environmental Protection Agency (EPA).

Additionally, GM agreed to write off greenhouse gas credits that equate to approximately 50 million tonnes of CO2, the EPA said, with a market value of hundreds of millions of dollars.

GM shares fell 0.51% Wednesday on the New York Stock Exchange.

Last year, GM paid the NHTSA a similar penalty of US$128 million when pick-up trucks sold several year prior failed to meet fuel economy standards.

In March, the Biden administration issued more stringent automobile emission standards for vehicles produced in the US.

The updated standards would progressively restrict the amount of emissions allowed as a way to incentivise automakers to pivot to producing more electric vehicles.