BERLIN — German prosecutors have widened a criminal investigation into Volkswagen’s Audi unit after authorities accused the luxury carmaker of installing a system designed to evade emissions rules in cars in Europe, a major shift for an inquiry that has previously concentrated on the United States.

The move, announced on Friday by authorities in Munich, adds to the troubles facing Volkswagen. The company has been hit by a wave of lawsuits and penalties after revelations in 2015 that it illegally used so-called defeat devices to pollute more than was allowed.

The automaker has already agreed to pay $22 billion in penalties and settlements in the United States and pleaded guilty to its vast emissions deception, which involved a variety of Volkswagen, Audi and Porsche-branded vehicles. Six Volkswagen executives face criminal charges in the United States. And the company is grappling with further legal action in Europe, where dozens of senior staff members — including its former chief executive — are being investigated.