(Adds details from complaint, case citation, stock price)
May 25 (Reuters) - General Motors Co was accused in a lawsuit on Thursday of rigging hundreds of thousands of diesel trucks with so-called "defeat devices," similar to those used by Volkswagen AG, to ensure they pass required emissions tests.
The proposed class-action lawsuit was filed in the federal court in Detroit on behalf of people who own or lease more than 705,000 Silverado and Sierra trucks fitted with "Duramax" engines from the 2011 to 2016 model years.
It alleged that GM used at least three different devices designed to ensure that its trucks would meet federal and state emission standards, even if they generated more pollution in real-world driving.
A spokesman for the Detroit-based automaker did not immediately respond to a request for comment.
GM shares fell as much as 3.8 percent after the lawsuit was filed. In early afternoon trading, they were down 93 cents, or 2.8 percent, at $32.27.
The lawsuit was filed by several law firms including Hagens Berman Sobol Shapiro, which was involved in similar litigation against VW and helped reach multi-billion dollar settlements with that automaker.
According to the complaint, emissions testing in real-world conditions conducted on behalf of the plaintiffs found that Duramax-equipped trucks produced NOx pollutants, comprised of nitrogen and oxygen atoms, two to five times higher than legally permitted.
The case is Fenner et al v General Motors LLC et al, U.S. District Court, Eastern District of Michigan, No. 17-11661. (Reporting by Jonathan Stempel in Chicago; Editing by Bernard Orr)