About 30 percent of North Korean defectors from areas near the Punggye-ri nuclear site have been found to show chromosomal mutations potentially linked to radiation exposure, the unification ministry's research showed Friday.

The fifth annual study, conducted last year, tracked 59 North Koreans who had lived in eight cities and counties near the nuclear testing site in North Hamgyong Province and defected to the South after the North's first nuclear experiment on Oct. 9, 2006.

Of those tested, 26 individuals showed chromosomal abnormalities that may stem from exposure to radiation released by the tests through water, air and other pathways. None of the subjects had cancers known to be associated with radiation exposure.

The ministry reported the findings to the National Assembly and revealed them to the press, while cautioning that the results do not rule out other possible causes, such as smoking, CT scans and other environmental factors.

Across the five years of testing, 64, or nearly 30 percent, of the total 214 North Korean defectors examined showed chromosomal mutations potentially tied to radiation exposure.

An official at the National Radiation Emergency Medical Center, which conducted the test, said it is scientifically reasonable to suspect the nuclear tests are responsible for the abnormalities seen in nearly 30 percent of subjects, and called for continued research to establish a clearer link.

About 800 North Koreans from the eight affected cities and counties have resettled in South Korea to date. This year's study aims to recruit 50 new participants and 10 returning subjects for follow-up testing.