Seven blocks of movable metal type that could have been the world's oldest are fake, South Korean authorities said Tuesday.

The seven were thought to have printed "Jeungdoga," a Buddhist song note from the Goryeo Dynasty (918-1392). If that were the case, the text from 1239 would have become the world's first document printed with movable metal type, replacing "Jikji," a Korean Buddhist scripture printed in 1377.

The seven blocks, however, are "highly likely" to have been fabricated, the National Forensic Service said.

"The inner and outer surfaces of the blocks yielded different CT scan results," a forensic official said. "It could be that the outer surface became rusty, but the corrosion does not seem to have progressed naturally."

Some of the straight lines were straighter than those on more recent metal type blocks from the 15th century, the official added.

There remain 102 other metal type blocks that could have been used to produce "Jeungdoga." One of them is preserved at the National Museum of Korea, while the remaining 101 are at the Daboseong Antique Shop, a gallery displaying ancient artifacts in central Seoul.

The Cultural Heritage Administration has been conducting its own study of the 102 blocks since June to determine their authenticity. The seven recently deemed fake were excluded because they weren't asked to be listed as South Korea's cultural properties. (Yonhap)