The U.S. Department of Energy previously listed South Korea as a sensitive country subject to restrictions on cooperation in nuclear power, energy and advanced technology during the 1980s and 1990s.

Citing a report by the U.S. Government Accountability Office, South Korea's Yonhap News Agency reported Monday that the country was on the list in the 1980s and early 1990s before being removed in July 1994, apparently in response to Seoul's request the previous year.

According to the department's website, countries may be included on the list due to national security concerns, nuclear nonproliferation issues, regional instability, threats to national economic security or support for terrorism.

While the news agency could not verify when South Korea was first included on the list, Lee Chun-geun, a visiting expert at the Korea Institute of S&T Evaluation and Planning, said the country is believed to have been first classified in 1981.

It is speculated that the former Park Chung-hee administration’s push for nuclear armament and the political upheaval following Park’s 1979 assassination may have led to the designation.

Seoul's foreign ministry said it was working to determine the relevant facts.

On Friday, a spokesperson from the department confirmed that the previous Biden administration placed South Korea in the lowest category of the list in early January.

Although the spokesperson said the inclusion does not prohibit scientific or technical cooperation between the allies, such cooperation would undergo an internal review beforehand.