Volkswagen was facing fresh questions on Tuesday after U.S. regulators widened their accusations of emissions- test cheating against the German carmaker to include the luxury Porsche brand previously run by its new CEO.<br />The U.S. Environmental Protection Authority said late on Monday VW used devices to rig air-pollution tests in 3.0-litre diesel engines mostly found in Audis and Porsches -- the company's biggest sources of profit.<br />Europe's largest carmaker had previously admitted to installing cheat software on up to 11 million vehicles worldwide with smaller diesel engines.<br />VW said on Monday "no software had been installed ... to alter emissions' characteristics in a forbidden manner" on the larger engines.<br />It did not immediately respond to questions on Tuesday, saying it would only correspond in writing.
