UPDATE: German Carmakers Also Backed Diesel Fume Tests on Humans

German carmakers are scrambling to distance themselves from the political fallout of research they backed that exposed 25 human test subjects to diesel exhaust fumes, Bloomberg News reports.

The revelation comes only days after a New York Times report linking the companies to similar tests in the U.S. with monkeys. The latter tests used diesel fumes from an engine Volkswagen AG had rigged to lower its emissions during such tests.

Both studies were conducted by the European Scientific Study Group on Environment and Health in the Transport Sector (EUGT). The now disbanded research and lobbying group was created by BMW, Daimler, VW and Bosch to produce scientific research favorable to the continued use of diesel engines.

The tests on humans were conducted at Aachen University in Germany. The university says the work was approved by an independent ethics board and focused on workplace pollution, according to Bloomberg.

VW Chairman Hans Dieter Poetsch describes the tests as “incomprehensible” and vows a full investigation. The prime minister of Lower Saxony, who sits on VW’s supervisory board, condemned both research studies as “absurd and abhorrent.”

The image of the diesel has nosedived since VW admitted in 2014 that it rigged 11 million of the engines to cheat on emission tests. Bloomberg notes that revelations about the diesel fume tests are certain to further undermine any effort to revive the technology as a viable power source for cars in the future.