http://story.news.yahoo.com/news?tmp...a_explosion_dc
SEOUL (Reuters) - A mushroom cloud up to 2.5 miles in diameter was seen after an explosion in a remote area of North Korea (news - web sites) near the border with China, Yonhap news agency reported on Sunday, quoting sources in Beijing.
The South Korean news agency said Thursday's blast in Kimhyungjik county in Yanggang province appeared to much worse than a train explosion that killed at least 170 people in April.
South Korean intelligence officials said they were monitoring the report, but declined detailed comment.
A U.S. official said Saturday it was unclear what had happened in North Korea and said there were various possible explanations for the report.