FRANKFURT (Reuters) – BMW (BMWG.DE) on Monday rejected a media report that said the software in certain diesel models shut off a gas filtering system in certain road conditions, leading to excessive nitrogen oxide (NOx) emissions.

German broadcaster ZDF’s program WISO and daily newspaper Tagesspiegel had earlier reported that tests by German environmental lobby group DUH showed that the BMW 320d model’s NOx emissions jumped significantly when the car’s speed was increased by 10 percent in road tests.

The Tagesspiegel report said DUH’s test showed that the vehicle, whose engine has a euro-6 diesel emissions standard, emitted an average of 470 mg/km when driven at speeds of up to 120 km/hr on a motorway. The Tagesspiegel report said DUH said this showed that the gas filtering system was being shut off by the engine software.

At lower speeds and on the test bed, the emissions were below the 80 milligram per kilometer limit, the reports said.

WISO and Tagesspiegel said DUH’s test results had been confirmed by testing firm TUeV Nord.

In response to the reports, BMW said its vehicles complied with the legal requirements and had not been manipulated.

“There are no activities of technical provisions to affect the test mode used to measure emissions – that means that our exhaust systems are active both on the test bed and in practice,” the group said in a statement.

Volkswagen’s (VOWG_p.DE) admission in 2015 that it cheated U.S. diesel emissions tests has led to scrutiny of diesel vehicles across the sector.