An analysis of test data suggests that the defeat device to manipulate emission levels could have an impact on the fuel efficiency of Volkswagen’s diesel vehicles sold in Korea, the government said Thursday.

While the data provided by the Environment Ministry and the Transport Ministry shows a high likelihood, more driving tests need to be conducted to conclusively prove it, an official told Yonhap news agency.

“We have concluded that there is a correlation,” the official was quoted as saying. “We will launch a probe into the fuel efficiency aspect of those cars in question.” Details of the investigation were not available.

It is known that the devise, if operated, could consume more fuel, meaning lower fuel efficiency. Officials believe that driving tests will show the difference in fuel efficiency.

The move came a month after the Environment Ministry concluded that some Volkswagen cars sold in Korea were involved in the same emissions-cheating scheme as those sold in the U.S. The German carmaker has already admitted that it installed defeat devices in 11 million vehicles worldwide to cheat diesel emissions tests.

After running the first round of tests, the Environment Ministry revoked certification for the tested models, banned their sale and ordered a recall of about 125,000 cars. The ministry also fined the German carmaker about 14 billion won ($12 million).

Vehicles subject to recall include those equipped with the “EA189” engine. The list also includes the Volkswagen Beetle and the Q5, Q3 and A4 of its Audi luxury brand.

Volkswagen is obliged to submit detailed recall plans to the Environment Ministry by Jan. 6.

The carmaker should also explain how it plans to improve emissions results and maintain fuel efficiency after removing software attached to show fake emissions level.

Despite the deepening distrust after the cheating scandal involving the German carmaker, Volkswagen’s Tiguan was named the best-selling foreign car in South Korea this year.

According to the Korea Automobile Importers and Distributors Association, Volkswagen Korea sold a total of 8,269 units of the Tiguan 2.0 TDI in January-November period this year. Affordable price offered by Volkswagen as part of its promotion efforts since September was seen as a major contributing factor for its outstanding sales performance. Tiguan was followed by A6 35 TDI of it luxury brand Audi with 6,349 units.

By Cho Chung-un (christory@heraldcorp.com)