Secretary of State Colin Powell says the United States believes a recent explosion in North Korea was, in his words, not a nuclear event. South Korean reports say a large mushroom-shaped cloud was caused by the explosion. VOA's Stephanie Ho reports from Washington.

Speaking on Fox News Sunday, Secretary Powell played down the severity of the North Korean explosion.

"We have seen reports of this explosion, but based on all the information that we have, it was not any type of nuclear event," he said. "We are trying to find out more about it, and what exactly it was, if anything, but it does not appear to be a nuclear event."

He said the United States is monitoring newspaper reports that there is activity going on at a potential North Korean nuclear test site.

"We have been watching it," he added. "We can not tell if it is normal maintenance activity, or something more."

Secretary Powell said North Korea is involved in de-nuclearization talks with five other countries, including the United States, China, South Korea, Japan, and Russia. He added that these other countries would also view a North Korean nuclear test with great alarm.