No 'smoking gun' from last month's North Korea nuclear test

VIENNA - A month after North Korea's nuclear test, a monitoring agency said on Tuesday it was highly unlikely to find any "smoking gun" radioactive traces from the blast, potentially leaving key questions about the device unresolved.
The lack of this kind of scientific evidence may make it difficult to determine what fissile material was used in the isolated Asian state's third nuclear test, which was detected by seismic monitors.
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which has a global network of monitoring stations designed to pick up radioactive traces emitted from tests, said it had yet to find any such signs.
"It is very unlikely that we will register anything at this point ... at this late stage," CTBTO spokeswoman Annika Thunborg said.
Thunborg did not give details, but the failure to detect radioactive traces could indicate that North Korea managed to prevent any such release from the February 12 underground explosion.