Volkswagen employees issued an apology after a test exposed monkeys to diesel fumes while the company was working on studying effects of the exhaust.
"We apologize for the misconduct and the lack of judgment of individuals," Wolfsburg, Germany-based VW said in a statement. "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."
The New York Times first reported the 2014 study, where it revealed researchers showed cartoons during the tests to help keep the monkeys calm.
The chairman of Volkswagen said the tests were "totally incomprehensible" and must be investigated fully.
The German government said auto emissions tests on monkeys are not justified.
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Volkswagen apologizes for using monkeys to test diesel fumes