FRANKFURT, Germany (AP) - The chairman of Volkswagen says that diesel exhaust tests involving monkeys were "totally incomprehensible" and the matter must be "investigated fully and unconditionally."

Monday's comments by Hans Dieter Poetsch, reported by the dpa news agency, come in the wake of a report by the New York Times that a research group funded by auto companies exposed monkeys to diesel exhaust from a late-model Volkswagen, while another group was exposed to fumes from an older Ford pickup.

The experiments were carried out in 2014 before Volkswagen was caught using software that let vehicles cheat on vehicle emissions. They were intended to show modern diesel technology had solved the problem of excess emissions.

The report was followed by one in the Stuttgarter Zeitung that the now-closed research group also experimented on humans.

Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.