A group dedicated to North Korean human rights issues claims that hundreds of thousands of North Korean residents living near the Punggye-ri nuclear test site may be exposed to radiation.

In a report Tuesday, the Transitional Justice Working Group presented the risk and effect of radioactive contamination of groundwater sources from the Punggye-ri test Site.

It said that over one million people live in the eight cities and counties within a 40 kilometer radius based on North Korea's 2008 census data.

Of this total, the report states those affected from the leakage and dissemination of the radioactive materials by water would be approximately 540-thousand or 270-thousand under the assumption that 50 or 25 percent respectively are affected.

It also suggested that smuggling and distributing agricultural and marine products may leave not only the North Korean people but also those in neighboring China, South Korea and Japan at risk.

The group called for a thorough investigation into the risk of groundwater contamination and disclosure of the findings and test results and also to strengthen inspection of agricultural and marine products from North Korea.

However some experts contend that such radioactive leakage is highly unlikely because the nuclear tests were conducted underground and most rocks at the site are granite.