German luxury carmaker BMW has been sued in the United States over "defeat devices" installed in tens of thousands of vehicles in order to cheat diesel emissions tests, lawyers for the plaintiffs said Tuesday.

The case, filed in federal court in New Jersey, will become a class-action suit once it is certified by a judge.

The suit singles out the BMW X5 and 335D model diesel cars sold between 2009 and 2013.

The attorneys at the Hagens Berman firm claim emissions from those cars were as much as 27 times higher than the standard allowed.

"At these levels, these cars aren't just dirty -- they don't meet standards to be legally driven on US streets and no one would have bought these cars if BMW had told the truth," said Steve Berman, the firm's managing partner.