FRANKFURT -- BMW said Friday that European Commission staff conducted an "inspection" at company offices in Munich earlier this week in connection with news media allegations that German carmakers colluded on technology including diesel emission controls.

BMW said it was assisting the European Union's executive arm in its work and that the inspection did not mean a formal antitrust investigation had been opened.

Der Spiegel magazine has reported that German car companies co-operated on issues including limiting the size of tanks holding fluid intended to reduce diesel emissions. The issue is getting attention because testing has shown that many diesel cars exceed pollution test standards in everyday driving.

BMW says its cars' exhaust emissions were never manipulated and that it has complied with all legal requirements.

The Commission said in a statement that it had conducted an "unannounced inspection" at a German automaker. Both the Commission and BMW statement avoided use of the word "search." The EU has said it is evaluating the media reports about collusion as a preliminary step to the possible opening of a full-fledged anti-trust probe.

The Commission said the inspection, which took place Monday, was "related to commission concerns that several German car manufacturers may have violated EU antitrust rules that prohibit cartels and restrictive business practices."