Nissan is being investigated, South Korean official Koh Sung-woo told Reuters, for overstating fuel economy numbers for the Infiniti Q50 by 3.4 percent.
"They manipulated the test results of the car to make the fuel economy look better," Koh said.
The transportation ministry's inquiry into Nissan has prompted the Seoul Central District Prosecutors' Office to launch its own investigation, after the ministry filed a criminal complaint.
It was unclear which Porsche and BMW models were under investigation. Representatives from the two companies in South Korea told Reuters they were unaware of the matter.
Nissan's Korean division chalked up the issue to problems with the official certification documentation provided to Sputh Korean officials in 2016, and a spokesperson told Reuters the company felt "sincere regret" over the matter.
BMW, Porsche, and Nissan have already taken heat from South Korean officials this year. Last month, the nation's environmental ministry banned 10 different models made by the three companies—including the BMW X5 M and the Porsche Cayenne and Macan sport-utility vehicles—for fudging documents related to noise and emissions levels.
Nissan is also being investigated by the country for reportedly using a defeat device to illegally alter emissions figures for the diesel-powered Qashaqi, a small SUV related to the Rogue.