South Korean officials said Thursday that they will investigate the fuel efficiency of Volkswagen vehicles whose emissions were manipulated to look as if they adhered to environmental regulations. The decision follows the South Korean transport ministry's finding last month that the automaker's estimated emissions and the fuel efficiency of its vehicles were connected.

Details on when and how the investigation will be conducted were not immediately clear, Yonhap reported, citing a government official close to the investigation. The environment ministry and the transportation ministry conducted their own investigations into the cheating on emissions tests by the German automaker. The transportation ministry’s analysis was aimed at determining how much of an impact manipulating the emissions could have had on fuel efficiency and, now, it is set to test the vehicles' fuel efficiency in a real-world driving test.

"We have concluded that there is a correlation," the official told South Korea’s state-run news agency Yonhap reported, adding: "We will launch an investigation into the fuel efficiency aspect of those cars in question."

Under South Korean rules, the company could face a fine and the cars can be recalled if the discrepancy in fuel efficiency tests exceeds 5 percent -- the cap set by the government.

Last month, South Korean officials fined the company $12.3 million and ordered the recall of 125,000 diesel vehicles that were found to be equipped with illegal, so-called “defeat devices” that produced a false reading on emissions tests.

The company will now be required to submit a detailed plan on recalls to the South Korean environment ministry by Jan. 6, describing how the company plans to maintain fuel efficiency after removing the “defeat devices.” 

Volkswagen has not yet commented on the latest decision of the South Korean ministry but a spokesperson for the company said that the company will "wait until the results of its planned investigation come out."

“Any details relating to future recalls will be determined after all the technical details necessary for the recall procedure have been confirmed and announced by our headquarters,” Volkswagen Korea reportedly said in November after the fine and the recall, adding: “We will take necessary measures based on legal procedures and requirements under the relevant laws and regulations.”

Also in November, the California Air Resources Board asked Volkswagen Group of America to recall some of its Volkswagen, Audi and Porsche brand vehicles sold in the state. Volkswagen has also reportedly set aside more than $7 billion to the help the company deal with the costs of the recall.