An advisory body of the UN Educational, Scientific and Cultural Organization(UNESCO) has reportedly deferred the nomination of controversial Japanese mines on the island of Sado as a World Heritage site, asking for additional documents.

The Japanese Agency for Cultural Affairs said on Thursday that the International Council on Monuments and Sites (ICOMOS) recommended the nomination for the mine complex be “referred” back to Japan for more information.

The World Heritage Committee evaluates site nominations based on the advisory body's decision and categorizes them into the same four categories — inscription, referral, deferral, or denial.

The committee, which consists of representatives from 21 state parties, will make the final decision at its meeting in New Delhi, India, in July.

Japan has pursued UNESCO registration of the mines on Sado Island, where Koreans were forced to work during World War Two, but has been criticized for intentionally leaving out any mention of forced labor in the mine. 

South Korea has called for a comprehensive reflection of the entire history of the Sado mine in the discussion of its potential inclusion as a UNESCO World Heritage site.