The mystery of a seventh century fresco in Uzbekistan that depicts foreign dignitaries from a number of countries, including the ancient Korean Goguryeo kingdom, has been unveiled by researchers.

South Korea's Cultural Heritage Administration said on Friday that it completed a scientific analysis of the wall painting from the Afrasiab Museum of Samarkand.

Through an on-site investigation of the fresco's preservation and management and a study of eleven fragments brought to South Korea last December, the agency said plaster was used along with lazurite for blue colors and red clay for red colors.

As for the black paint, a mineral containing lead was found to have been used for the first time, rather than ink, which is often used in Korean traditional paintings.

Researchers expect the latest discovery to assist their study of the distribution channel of mural and coloring techniques between the Korean Peninsula and Central Asia, as well as art preservation efforts.

During President Moon Jae-in's visit to Uzbekistan last year, the two countries agreed to conduct research and to work together to preserve the artifact.