FRANKFURT — Germany’s high-end carmakers face a potentially destructive new scandal after European antitrust authorities said on Saturday that they were looking into allegations that Volkswagen, Daimler and BMW colluded illegally to hold down the prices of crucial technology, including emissions equipment.

If proven, the allegations threaten to further damage the country’s reputation for engineering excellence. That reputation has already been badly tarnished by Volkswagen’s admission that it illegally installed software in its diesel-powered cars to evade standards for reducing smog. The emissions scandal, which came to light nearly two years ago, may now be spreading to rivals.

Growing awareness of the harmful effects of diesel fumes has prompted European cities to consider bans of diesel cars and has led consumers to reject cars with diesel engines, a largely German innovation that traditionally accounted for half the market.

The backlash could take on a new, far broader dimension if it turns out that the excess emissions were the result of illegal collusion by a de facto cartel. The investigation could also lead to billions of euros in fines.