Motorcycle giant Harley-Davidson on Thursday entered a $15 million settlement with US authorities who accused the company of making and selling illegal devices that increased air pollution from its bikes.

The company, the iconic American manufacturer large and loud motorcycles, agreed to buy back and cease selling so-called ‘super tuners,’ which improved performance but increased hydrocarbon and nitrogen oxide emissions.

The company has produced and sold about 340,000 of the devices, which are prohibited under the US Clean Air Act, the Justice Department said.

The announcement comes as the German automaker Volkswagen faces continuing legal woes after admitting that it had installed emissions cheating devices on 11 million diesel-powered automobiles worldwide.

Last year, the company sold about 265,000 motorcycles worldwide and 168,000 in the US.

Assistant Attorney General John Cruden, head of the Justice Department's Environment and Natural Resources Division, said in a statement that other manufacturers should consider themselves warned.

‘Anyone else who manufactures, sells or installs these types of illegal products should take heed of Harley-Davidson's corrective actions and immediately stop violating the law,’ Cruden said.

The settlement involves both the Justice Department and the US Environmental Protection Agency.

Under its terms, Harley will pay a $12 million civil penalty and devote another $3 million to a project to replace conventional woodstoves with cleaner-burning stoves in local communities, according to the statement.