Volkswagen and its Audi unit froze sales of diesel car models in the United States Wednesday after new accusations on the use of software that cheats on emissions tests.
The move came after another Volkswagen unit, Porsche, halted sales of its Cayenne diesel sport utility vehicles following the new allegations from the Environmental Protection Agency.
The EPA said Monday that VW, Audi and Porsche cars with 3.0 liter diesel engines were equipped with illegal "defeat devices" which cover up excessive emissions of poisonous gases when the vehicles undergo pollution testing.
Prior to that the company had admitted only that its 2.0 liter diesel engines had defeat devices, and following the EPA's announcement Volkswagen denied the larger engines were similarly equipped.
The new sales freeze covers diesel VW Touaregs, Audi A6, A7 and A8s, and Q5 and Q7s, all from the 2014-2016 model years.
"We are just being more proactive," said Audi spokesman Bradley Sterz.
"The difference here is that we are not entirely clear on what data the agency used to come out with this notice of violation. We want to understand how the regulator made its conclusions."