Seoul, Shares in Hyundai Motor and its affiliate Kia plunged on Wednesday, as German authorities raided the carmakers' local offices over suspicions they had installed defeat devices on some of their combustion cars.

On Wednesday, Hyundai plunged 5.7 per cent to 175,500 won ($135.17), and Kia plummeted 6.1 per cent to 76,900 won.

Among other affiliates, auto parts maker Hyundai Mobis Co. fell 3.6 per cent to 199,000 won, and logistics firm Hyundai Glovis Co. shed 1.1 percent to 183,000 won, reports Yonhap news agency.

Hyundai confirmed the raid by German prosecutors, and it is working with the German authorities about the matter. It didn't elaborate on the investigation.

Defeat devices are mechanisms or software that can change vehicle emissions levels. Carmakers may use the devices to cheat on emissions tests.

Hyundai and Kia allegedly placed more than 200,000 diesel vehicles with suspected illegal defeat devices in the German market, according to foreign news media reports.

Germany has investigated carmakers operating in the country over possible manipulation of emissions in their combustion vehicles. Hyundai is one of the subjected companies, though the investigation could be expanded, people familiar with the matter said.

In South Korea, Volkswagen has struggled with weak sales due to the impact of the emissions cheating scandal that began in September 2015, when the United States discovered the German carmaker cheated on its local diesel emissions tests.

In July 2016, the group "voluntarily" stopped selling its vehicles in South Korea, as the Seoul government announced it would ban the sale of all Audi and Volkswagen cars, and impose heavy fines for emissions cheating.

The German carmaker, which sells vehicles under four brands -- Audi, Volkswagen, Lamborghini and Bentley -- resumed sales in Korea in early 2018.