Authorities in Germany have raided BMW’s Munich headquarters and its engine plant in Austria as part of an investigation into the alleged use of emissions cheating software. According to officials, 11,400 BMW 750d and BMW M550d vehicles are involved in the issue.

“There is an early suspicion that BMW has used a test bench-related defeat device,” prosecutors said in a report by the BBC. This comes following BMW’s revision of CO2 figures for its entire range under the new Worldwide Harmonised Light Vehicles Test Procedure (WLTP), which were considerably higher than following the previous New European Driving Cycle (NEDC) test.

In an official statement, BMW said it is taking the situation very seriously and will work closely with the relevant authorities. “The BMW Group continues to assume that the situation was caused by an incorrect allocation of the software and does not represent a deliberate attempt to manipulate exhaust emissions,” it said.

The carmaker has since recalled 11,700 vehicles for software changes, but Germany’s Federal Motor Transport Authority (KBA) said that it didn’t consider the software used in affected models to be a defeat device.

“Many of the affected vehicles were initially sold with the correct software and ran correctly for over two years. The incorrect software was employed a significant time after these models originally started production,” BMW stated.