Volkswagen has said it found "unexplained inconsistencies" in the carbon dioxide emissions for 800,000 more cars, the latest blow for the troubled automaker already in crisis from an emissions scandal.
The German company said on Tuesday it could take a $2.2bn hit after understating the level of fuel consumption and carbon dioxide emissions for some of its models, including petrol-run vehicles for the first time.
The disclosure is the latest in a string of problems identified with Volkswagen emissions, which have caused the company's share prices to plummet.
Related: VW suffers $3.9bn quarterly loss over emissions scandal
In September, the company admitted installing software in 11 million cars around the world in order to evade diesel emissions testing. It has already set aside $7.4bn to cover the costs of recalling those vehicles.
The so-called irregularities revealed on Tuesday, which were uncovered during an internal investigation, apply mostly to smaller diesel engines.
The models affected are Volkswagen Polos, Golfs and Passats, Audi A1 and A3 models, Skoda Octavias, and Seat Leons and Ibizas, a Volkswagen spokesperson told the DPA news agency.
He added, however, that a smaller number of petrol-run engines with cylinder cut-offs are also affected.
Volkswagen said the safety of the cars in question "is in no way compromised", adding that it "will endeavor to clarify the further course of action as quickly as possible and ensure the correct CO2 classification for the vehicles affected" with the responsible authorities.
"From the very start I have pushed hard for the relentless and comprehensive clarification of events," Volkswagen Chief Executive Matthias Mueller said in a statement. "We will stop at nothing and nobody. This is a painful process but it is our only alternative."
The latest findings come a day after US regulators said the Wolfsburg-based company had installed software on thousands of its luxury brands - Porsche and Audi - to cheat pollution tests.
Volkswagen has denied the allegations, but faces the prospect of more fines and lost sales.
The biggest business crisis in VW's 78-year history has wiped as much as a third off its stock market value, forced out long-time CEO Martin Winterkorn and rocked the auto industry, a key employer and source of export income in Germany.