The South Korean government has said it may ban six car models sold by three foreign automakers in the country after it found issues with the certification documents used to obtain sales permits, according to local reports.

The three brands affected are BMW, Porsche and Nissan, following an investigation launched in August into the approval of imported brands in the country in the wake of the Volkswagen-Audi emissions/fuel efficiency scandal.

Earlier this year the government withdrew the local sales permits for about 80 Volkswagen and Audi models after it found that homologation documents had been falsified. This inevitably resulted in a sharp drop in local sales of the two brands.

The Ministry of Environment is reported to have found issues with the certification documents of 10 vehicle models imported by the three brands, four of which are no longer on sale in the country.

The six current models affected are the BMW X5M; Nissan Qashqai and Infiniti Q50; plus Porsche Macan S Diesel, Cayenne S E-Hybrid and Cayenne Turbo models.

Local reports suggest Nissan used Renault engine test results for Qashqai homologation and Mercedes-Benz certificates for the Q50 - both automakers were the original developers of the engines.

Similarly, BMW put forward engine test results relating to its X6M, which has the same engine as the X5M, and maintains that these should be applicable.

Porsche, which is accused of modifying emission test reports, said it was co-operating fully with the investigation and that it had already voluntarily suspended sales of the three models.

The cases of three automakers are scheduled to be heard in mid-December.