Frankfurt: Former Volkswagen AG chief executive officer Martin Winterkorn was notified as early as May of 2014 that US authorities would probably inspect the company’s cars for an emissions-test defeat device, according to German newspaper Bild am Sonntag.

A VW employee wrote to Winterkorn to say that the carmaker couldn’t provide an explanation for elevated nitrogen oxide emissions and that the authorities would probably look for a test-recognition function in motor-steering software, the German newspaper reported, citing a company document. Bild didn’t identify the employee.

VW admitted in September that it had rigged some diesel engines so that emissions controls came on only during testing. Those controls shut off while the car was on the road, producing nitrogen oxide well in excess of the US legal standard. Europe’s largest automaker now faces damage to its reputation as well as penalties that could stretch into the billions of dollars.

Winterkorn declined to comment, according to Bild. A lawyer for the former CEO didn’t answer a call from Bloomberg outside of normal office hours and didn’t immediately respond to an e-mail seeking comment.

Eric Felber, a VW spokesman, declined to comment on the report. The company’s investigation into the matter will be concluded in the second half of April, he said.

Separately, Bild cited German transport minister Alexander Dobrindt as saying VW has to win back trust globally.

“It’s important that those responsible be clearly named and made accountable," the minister was cited as saying in an interview, without referring to Winterkorn. Bloomberg