A U.S. military satellite recently detected signs of an "imminent" test at North Korea's nuclear detonation site, the Korea Herald reported on Tuesday.
An unidentified senior U.S. official told CNN that a tarpaulin was spotted late last week covering one of the tunnel entrances at the Punggye-ri test site. Pyongyang employed a similar tactic to cloak its test preparations shortly before it carried out its most recent nuclear detonation in February 2013.
South Korean officials said it is still not clear if North Korean workers have moved to begin sealing the tunnel entrance with dirt or cement, which is done to minimize the release of radioactive emissions following an underground atomic blast. That step is typically one of the last to come before a nuclear trial.
The final sign of an imminent test will probably be when Pyongyang clears the site of all personnel and vehicles, according to 38 North. A Friday analysis by the expert website concluded that recently detected new excavation work at a separate part of Punggye-ri indicated that a nuclear detonation was not imminent. The assessment was based on the belief that North Korea would unlikely begin a new substantial phase of its expansion of the site while at the same time planning a test in the immediate future.
South Korean Foreign Minister Yun Byung-se in a speech in New York City said if North Korea proceeds with its stated plans for a new kind of atomic detonation, "it will have to pay the highest price, one that it has never experienced."
"Our assessment is that North Korea is ready to undertake a test whenever they make the necessary political decision," Yun was quoted by the Associated Press as saying.