Three top German auto companies -- Daimler, BMW and Volkswagen -- came under scrutiny after media reports last week revealed that they funded an organization called the European Research Group on Environment and Health in the Transport Sector (EUGT), presstv.ir reported.
EUGT, in turn, financed experiments which saw humans and monkeys exposed to diesel fumes that have been linked to asthma, lung diseases and heart attacks.
In reaction to the criticism, Daimler said it fired the executive who represented it at EUGT.
The sacked executive sat on the top management board of the now-dissolved EUGT entity, Daimer said in its statement on Wednesday.
BMW, for its part, said its representative on the EUGT's management board would be removed from his current functions pending an investigation into the research group's work by the carmaker's legal experts, adding that he would remain with the Munich-based carmaker.
Daimler and BMW did not give the names of the affected employees.
Earlier, Volkswagen said on Tuesday it had suspended its head of external relations, who said he knew about the experiments but did not inform the company's then-CEO, Martin Winterkorn.
Despite the controversial tests that exposed monkeys to toxic diesel fumes in a US lab in 2015, German carmakers made huge profits in 2017.