FRANKFURT (Reuters) - A research organization funded by German carmakers sponsored scientific experiments testing nitrogen dioxide, a gas found in exhaust fumes, on people, German daily Stuttgarter Zeitung said.

The European Research Group on Environment and Health in the Transport Sector, EUGT, commissioned the study, the paper said.

Reuters could not immediately confirm the details of the study and a representative for EUGT, which was dissolved last year, could not be reached for comment.

The research organization received its funding from German carmakers Volkswagen VOWG_p.DE, Daimler and BMW.

The purpose and outcome of the study remain unclear but revelations about experiments involving people come as the auto industry faces bans of toxic diesel vehicles from inner cities following revelations in 2015 that Volkswagen manipulated emissions on diesel-engined cars.

Stuttgarter Zeitung said around 25 healthy young people inhaled nitrogen dioxide in varying doses over a period of hours at an institute belonging to Aachen University in Germany.

The impact of the gas on people could not be determined when the study was published in 2016, Stuttgarter Zeitung said.

Daimler on Sunday condemned the studies, done by the same research body which sponsored another experiment forcing monkeys to inhale toxic exhaust fumes from a polluting diesel Volkswagen equipped with illegal software.

“We are appalled by the extent of the studies and their implementation. We condemn the experiments in the strongest terms. Even though Daimler did not have influence on the study’s design, we have launched a comprehensive investigation into the matter,” Daimler said in a statement on Sunday.

The New York Times on Friday said the scientific study involving monkeys was conducted in 2014. BMW, Daimler and VW have condemned the emissions experiments involving monkeys.

The New York Times said EUGT had commissioned a study to defend the use of diesel after the World Health Organisation said the fuel’s exhaust fumes were carcinogenic.