BERLIN (AP) — A German government commission is seeking further explanation from General Motors Co.'s Opel division of diesel engines that can disable some pollution controls under certain circumstances.

Opel representatives appeared Wednesday before the panel looking into diesel emissions controls, following a report last week by German environmental group DUH and the weekly Der Spiegel that the Zafira model reduces pollution controls at some speeds and temperatures.

Transport Minister Alexander Dobrindt said the company acknowledged that some controls are reduced above 145 kph (90 mph) and below a certain air pressure in order to protect the engine, an explanation about which the panel had questions. He noted that defeat devices or shutdown systems aren't allowed unless they're necessary to protect the engine.

Opel is to submit technical details within two weeks.

"Opel stressed to us today that they are within the framework of the law with the measures they described," Dobrindt said. "On two points, we told the Opel representatives that we have doubts as to whether these measures fully serve protecting the engine."

The automaker strongly denies doing anything illegal.

Opel CEO Karl-Thomas Neumann said after Wednesday's meeting that "Opel engines conform with the law and we have no illegal software." He said the company will "fully and cooperatively support" the panel's examination of the case.