FRANKFURT, Germany — In 2014, as evidence mounted about the harmful effects of diesel exhaust on human health, scientists in an Albuquerque laboratory conducted an unusual experiment: Ten monkeys squatted in airtight chambers, watching cartoons for entertainment as they inhaled fumes from a diesel Volkswagen Beetle.

German automakers had financed the experiment in a bid to prove that diesel vehicles with the latest technology were cleaner than the smoky models of old. But the American scientists conducting the test were unaware of one critical fact: The Beetle provided by Volkswagen had been rigged to produce pollution levels that were far less harmful in the lab than they were on the road.

The results were being deliberately manipulated.

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The Albuquerque monkey research, which has not been previously reported, is a new dimension in a global emissions scandal that has already forced Volkswagen to plead guilty to federal fraud and conspiracy charges in the United States and to pay more than $26 billion in fines.

The company admitted to installing software in vehicles that enabled them to cheat on emissions tests. But legal proceedings and government records show that Volkswagen and other European automakers were also engaged in a prolonged, well-financed effort to produce academic research that they hoped would influence political debate and preserve tax privileges for diesel fuel.

The details of the Albuquerque experiment have been disclosed in a lawsuit brought against Volkswagen in the United States. The organization that commissioned the study, the European Research Group on Environment and Health in the Transport Sector, received all of its funding from Volkswagen, Daimler and BMW. It shut down last year amid controversy over its work.

The organization, known by its German initials EUGT, did not do any research itself. Rather, it hired scientists to conduct studies that might defend the use of diesel. It sponsored research that challenged a 2012 decision by the World Health Organization to classify diesel exhaust as a carcinogen. It financed studies that cast doubt on whether banning older diesel vehicles from cities reduced pollution.

Volkswagen, Daimler and BMW said the research group did legitimate scientific work. “All of the research work commissioned with the EUGT was accompanied and reviewed by a research advisory committee consisting of scientists from renowned universities and research institutes,” Daimler said.

Daimler and BMW both said they were unaware that the Volkswagen used in the Albuquerque monkey tests had been set up to produce false data. Volkswagen said that the researchers had never managed to publish a complete study.

It wasn’t for lack of trying.

Documents produced in legal proceedings show that in August 2016, Michael Spallek, the director of the automakers’ research group, emailed the Lovelace Respiratory Research Institute, the Albuquerque organization that conducted the tests with monkeys. “The EUGT point of view is that it’s time to try to finalize the report and to present or discuss the problems of the study in a scientific way ASAP,” Spallek wrote.

That was almost a year after Volkswagen admitted to equipping millions of diesel vehicles sold in the United States and Europe with illegal “defeat devices” that cranked up pollution controls when software detected that testing was being done in a lab.

Spallek declined to comment, saying his contract prohibits him from discussing the research group’s work.

The Albuquerque tests were conducted in 2014 using 10 cynomolgus macaque monkeys, a breed used extensively in medical experiments, according to the legal records.

Volkswagen took a lead role in the study. Company engineers supervised the installation of a treadmill that would allow the vehicles to run on rollers while equipment sucked exhaust from the tailpipes.

Jake McDonald, the Lovelace scientist who oversaw the experiments, said he did not know the Volkswagen Beetle was equipped with software that recognized when the car was being tested on a treadmill. The software cranked up controls so that nitrogen dioxide pollution was only a small fraction of what it would be during normal driving.

During his deposition, McDonald testified that he had not followed the Volkswagen case closely and had realized only recently that the Beetle used in the tests was manipulated to produce artificially low emissions.

“I feel like a chump,” McDonald said.

Jack Ewing is a New York Times writer.