WASHINGTON (REUTERS) - US environmental regulators on Monday said Volkswagen AG had installed emissions-control cheating devices in diesel luxury vehicles in model years 2014 through 2016.

The move pulls Volkswagen's luxury brands, Porsche and Audi, deeper into the emissions cheating scandal that has engulfed the Volkswagen brand. The EPA said the new investigation centres on 3.0 litre engines used mostly in larger, more expensive models.

Among the diesel models officials named as being in violation of US laws are the Porsche Cayenne sport utility vehicle and five Audi models, including the A6 sedan and the Q5 SUV.

Volkswagen admitted in September it had installed software, known as defeat devices, in 11 million cars around the world that can evade emissions tests.

The emissions cheats allowed the vehicles to pass tests meant to monitor vehicles' emissions of nitrogen oxide - a smog-causing pollutant.

The "defeat devices bypass, defeat or render inoperative elements of the vehicles' emissions control system", the EPA said in a letter to manufacturers.