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FRANKFURT (Reuters) - The European anti-trust watchdog plans to send formal complaints to BMW, Daimler and Volkswagen this spring, in which the EU regulator will make detailed allegations regarding collusion on emissions of diesel engines, Handelsblatt reported on Wednesday.

In a so-called “Statement of Objections” the EU is expected to detail its allegations, which may result in fines for the carmakers.

According to Handelsblatt, files from the public prosecutor’s offices in Braunschweig and Munich show that the carmakers cooperated on exhaust emissions and warned each other not to show the details of the work to the authorities. Daimler reported itself to the EU Commission in 2014, followed by Volkswagen two years later.

The EU Commission and Daimler had no immediate comment. BMW declined to comment. Volkswagen also said it was unable to comment on the audit.

“The Volkswagen Group and the respective Group brands have cooperated fully with the European Commission and will continue to do so,” it added.