Volkswagen has apologised for a study that used monkeys to test the health effects of inhaling diesel fumes.
Ten of the animals were forced to breath in fumes as part of an attempt to prove that new engines were cleaner.
The monkeys were shown cartoons during the tests to help keep them calm.
The experiments were carried out in 2014, before Volkswagen was caught using software that let vehicles cheat emissions tests.
Volkswagen Chairman, Hans Dieter Poetsch, has described the experiments on monkeys as “totally incomprehensible”.
The company has apologised for "the misconduct and the lack of judgment of individuals".
“We’re convinced the scientific methods chosen then were wrong. It would have been better to do without such a study in the first place", a statement read.