An official with the United States’ Environmental Protection Agency has reportedly told the Detroit News that vehicles powered by the Volkswagen Group’s 3.0-litre V6 diesel engine are being tested for potential exhaust emissions irregularities.

The 3.0 TDI engine powers multiple models which are sold in North America, including the VW Touareg and Porsche Cayenne as well as versions of the Audi A6, A7, A8 and Q7.