It said that in 2014, EUGT had exposed 10 monkeys to fumes - in an air-tight chamber - from several cars, including a diesel VW Beetle. The testing took place at a lab in Albuquerque, New Mexico.
Then at the weekend Germany's Stuttgarter Zeitung and SWR radio reported that 19 men and six women had inhaled diesel fumes in another EUGT experiment.
During a month of tests at a lab in Aachen, west Germany, they were exposed to various concentrations of diesel fumes, which contain toxic nitrogen oxides (NOx). The BBC has not seen the study itself, but German media say it was published in 2016.
At the time the carmakers were arguing that modern technology had cut pollution from diesel engines to safe levels. But VW was later found to have fitted "cheat" devices that rigged the emissions data.
