A Japanese daily says that many of the ancient royal books of Korea's Joseon Dynasty stored at Japan's Imperial Household Agency may not be originals.

Japan, which took the texts during its colonial rule of Korea early in the 20th century, has agreed to return over 12-hundred of the ancient books to Seoul.

But the Asahi Shimbun says that experts insist that 167 of the 12-hundred books are in fact copies and that the originals could be in a third country.

The Imperial Household Agency says it has documented evidence that copies of many of the Korean royal books were made to prevent a loss of the originals and that some of the copies were sent to Japan.

Asahi also quoted Korean experts as saying that the books were kept in two sets, one for the archives and one for presentation to the king. The experts said that many of the books in Japan appear to be for archive purposes.