The U.S. Environmental Protection Agency confirms asking Mercedes-Benz to explain its cars’ emission levels. Although, on Monday, the government office said it really has not started an official investigation.

The request for data – first reported by German newspaper Handelsblatt and later confirmed by EPA spokesperson Laura Allen – followed the class-action lawsuit filed against the carmaker by a BlueTEC owner, who alleged that the said Mercedes cars contain a device shutting off a nitrogen oxide-reducing mechanism in its exhaust.

The lawsuit argued that Clean Diesel vehicles are knowingly pre-programmed to emit higher nitrogen oxide levels that permitted by the law. The NOx levels are believed to be at levels 65 times higher than allowed by the EPA when operating in a temperature below 50 degrees Fahrenheit.

It accused the car manufacturer of false representations of the BlueTEC, which is promoted as “the world’s cleanest and most advanced diesel.”

The lawsuit against the car brand’s parent company Daimler AG was filed last Feb. 18 by law firm Hagens Berman before the New Jersey District Court.

Last Sunday, a Daimler spokesperson affirmed its full cooperation with the EPA’s information request, adding that all Mercedes-Benz cars comply with rules and regulations.

“All our vehicles comply with regulatory frameworks,” spokesman Joerg Howe says in response to the suit.

Daimler explained that there are certain cases when a system for treating exhaust fumes could work with reduced effectiveness in order to prevent the buildup of condensation. It further explained that condensation could otherwise cause corrosion and damage to the engine and exhaust system.

The suit against Mercedes-Benz occurs only five months after Volkswagen admitted tampering with the software in its diesel engine cars to cheat emission tests.

The Volkswagen scandal had begun tainting the reputation of diesel engines, previously known for their eco-friendliness. Back in January, Renault SA stocks plunged due to sudden investigations from French authorities, with the probe prompting a recall of 15,000 cars to ensure compliance with emissions rules.

Daimler, however, expects another record year in 2016, following its record volume of more than 2 million passenger cars around the world last year. Including medium and heavy trucks, unit sales reached nearly 2.9 million.

January is Mercedes-Benz cars’ 35th consecutive month marked by record sales.