Volkswagen, the “Peoples’ Car” founded in Germany in the 1930s, carried out rigged tests of their emissions that caused an international scandal three years ago.

But the fallout continues, beyond the criminal accusations and recalls. Now, accounts have emerged that the corporation subjected monkeys – and even humans – to exposure tests as the carmaker attempted to make the diesel exhaust, and especially nitrogen dioxide within it, appear safer than they truly are.

The 10 monkeys were placed in sealed chambers in front of TVs showing them cartoons, as Volkswagen Beetles drove on a treadmill, and their diesel fumes were pumped into the breathing spaces. The tests, conducted in 2014, were first revealed last week by The New York Times, which had acquired accounts of the trials from lawsuits filed in the United States.

But over the weekend, the German newspaper Sueddeutsche Zeitung unearthed further reports indicating that nitrogen dioxide tests were carried out in humans around the same time.

The tests were helmed by the European Research Association for Environment and Health in the Transport Sector, known by its German acronym of EUGT, according to the German account. The EUGT is a research group founded by the three major German auto manufacturers, Volkswagen and BMW and Daimler.

Both the monkeys tests and the human trials determined the respective exposures were not harmful to primate health. However, the exhaust pumped into the monkeys’ chambers appears to have been subject to the same software programming that allowed the cars to automatically sense it was a laboratory test setting – and to therefore emit less toxic gases than would normally have occurred in regular road driving.

Volkswagen “distances itself clearly from all forms of animal abuse,” the company reportedly said in response to the trials involving monkeys. They have not yet responded to the news of the human experiments. Daimler, for its part, said it “condemn(s) the experiments in the strongest terms,” and was “appalled by the extent of the studies and their implementation.” Furthermore, they said they have launched a “comprehensive investigation,” they added.

The monkey tests took place at the Lovelace Respiratory Research Institute in New Mexico in 2014, even as the extent of the Volkswagen emissions scandal was becoming clear. The New York Times reports how the Lovelace breathing experts had trouble finalizing their research, despite pressure from EUGT to do so. (The EUGT has since been shuttered by the car companies).

The human trials involved 25 healthy people. Their conclusion to the exposures: no discernible reaction to the inhaled nitrogen dioxide could be detected – including no inflammation in the respiratory tracts of the participants.

The Sueddeutsche Zeitung further reports that the monkey tests in New Mexico were originally intended to be conducted on humans – but backed off since the World Health Organization had previously classified diesel exhaust as carcinogenic.

Volkswagen admitted in 2015 to rigging tests in its pursuit of pushing “clean diesel” to car buyers. Volkswagen “defeat devices” installed sold in 11 million cars worldwide between 2008 and 2015 will lead to 1,200 premature deaths in Europe alone, according to one health estimate. Last January, the U.S. Department of Justice announced Volkswagen would plead guilty to multiple charges, and pay more than $4 billion in criminal and civil penalties. Six executives of Volkswagen were indicted on criminal charges for the alleged emissions conspiracy, as part of the ongoing investigation.