UN detects possible signs of past North Korea nuke test

VIENNA – A U.N. agency tasked with looking for signs of nuclear explosions says its monitoring stations have detected radioactive gases that could be linked to North Korea's Feb. 12 test.

CTBTO says stations in Japan and Russia have picked up "significant" traces of noble gases that accompany a nuclear explosion and say they "could be attributed" to the North's test.

A statement from the Vienna-based CTBTO Tuesday said the Japanese station is located around 600 miles from the test site. It says lower levels were picked up by the Russian site at Ussuriysk, without giving its location in relation to the site.

It says the two types of xenon radioactive isotopes detected "provide reliable information on the nuclear nature of the source."