But the company nevertheless used 'defeat device' software designed to reduce nitrous oxide emissions during laboratory testing while allowing up to 40 times the legal limit during real driving conditions. Neither complaint explicitly states that either man knew or authorised the use of the deceptive software.
A Volkswagen spokesman said there was "no credible evidence" to support the allegations against Mueller and called into question whether New York and Massachusetts authorities had identified the right person.
The two states' complaints cite testimony according to which the individual cited is indeed Matthias Mueller. Mueller was a project manager at Audi in 2006 when word allegedly reached him and Winterkorn - then CEO of Audi and later VW chief executive - that engineers were having difficulty meeting US emissions standards, according to the complaints. Mueller replaced Winterkorn as CEO when the latter resigned last year as a result of the scandal.