FRANKFURT — The German carmakers BMW and Daimler said on Wednesday that they had taken action against executives involved in an organization that sponsored emissions experiments on monkeys, as the companies tried to squelch a public outcry that threatens to tarnish the image of Germany’s most important exports.
The executives, who were not publicly identified, belonged to the board of an organization established by BMW, Daimler and Volkswagen. The group commissioned research intended to play down the health risks caused by diesel exhaust.
Details of the research, reported last week by The New York Times, have called attention to questionable methods employed by the car companies in trying to influence the public debate. On Tuesday, Volkswagen said it had suspended its chief lobbyist, Thomas Steg, amid the mounting furor over the experiments.
Even before the monkey research came to light, the carmakers had been struggling to stem a decline in diesel vehicles’ share of the European market, which is at its lowest point in a decade.
The falloff began after Volkswagen was caught in 2015 using software to conceal excess emissions by its diesel cars. The resulting scandal highlighted the health hazards of diesel exhaust. Public outrage has been further inflamed — and has spread to BMW and Daimler — by the carmakers’ use of monkeys as test subjects in what was effectively a marketing campaign.
Volkswagen, which has pleaded guilty to criminal charges in the United States in connection with the emissions-cheating scheme, continues to suffer legal consequences from the matter. On Wednesday, law enforcement authorities from Munich raided the homes of former employees of Audi, Volkswagen’s luxury car unit. Some Audi vehicles also contained the emissions-masking software.
Andrea Mayer, a Munich prosecutor, said the homes that were raided belonged to middle managers and were searched as part of an investigation into emissions cheating. Prosecutors have identified 13 suspects, Ms. Mayer said, but have not yet filed criminal charges against any of them.
The monkey experiments were paid for and overseen by the European Research Group on Environment and Health in the Transport Sector, known by its German initials, E.U.G.T. BMW, Daimler and Volkswagen financed the organization and all three companies had representatives on its board.
The research took place at the Lovelace Respiratory Research Institute in Albuquerque in 2014. Researchers there exposed one group of the monkeys to exhaust from a late-model diesel Volkswagen; a second group was exposed to exhaust from an older Ford diesel pickup truck.
Using monkeys as experiment subjects was not illegal, but it has angered animal-rights advocates and others who say the tests lacked the usual justification for research on primates, which is to advance medical science and protect human lives. In this instance, the monkeys were being used to try to help the companies sell diesel cars by showing that emissions were less harmful than many scientists had maintained.
The research suffered from procedural flaws and had not been published by the time the E.U.G.T. folded last year.
A separate project financed by the carmakers subjected human volunteers to doses of nitrogen dioxide, one of diesel’s most noxious byproducts. The research, in 2015, was authorized by an ethics commission at the RWTH Aachen University in Aachen, Germany, where it took place.
Daimler said Wednesday it had suspended its representative on the E.U.G.T. board. The company did not disclose his name, but a report by the organization summarizing its activities from 2013 to 2015, said the carmaker was represented by Udo Hartmann, whose title was head of Daimler’s group environmental protection and energy management.
Mr. Hartmann could not be reached for comment late Wednesday.
Daimler continued to try to distance itself from the monkey testing, in which Volkswagen employees took a leading role.
“Even though Daimler did not have influence on the study’s design, we have launched a comprehensive investigation into the matter,” the company said in a statement Wednesday. “We will fully investigate the facts, and make sure that such things do not happen again.”
BMW said its representative on the E.U.G.T. board had been “relieved of his current tasks” while the company conducted an internal investigation. The man remains a BMW employee, the company said.
According to the E.U.G.T. report about the organization’s activities from 2013 to 2015, BMW’s representative on the board at the time of the monkey research was Frank Hansen, a member of a company team that works on car-sharing and other new forms of urban transportation.
Mr. Hansen did not immediately respond to a request for comment. BMW implicitly defended his conduct on Wednesday, saying in a statement that the employee has provided credible assurances “that he critically called into question the commissioning of animal tests during his mandate on the board.”