North Korea cloud 'not nuke blast'
SEOUL, South Korea (CNN) -- A large cloud that appeared over North Korea in satellite images several days ago was not the result of a nuclear explosion, according to a U.S. official.
South Korea's Yonhap news agency is reporting a huge explosion shook North Korea's northernmost province on Thursday producing a mushroom cloud over 4 kilometers (two miles) wide.
The blast coincided with the anniversary of North Korea's founding on Sepember 9 when various military activities are staged.
The U.S. official said the cloud could be the result of a forest fire.
South Korea's Unification Minister Chung Dong-yong said the government was aware of the reports and is checking them.
"I have no information about the size of the damage of the explosion," he said on Sunday, according to Yonhap.
Chung also said he believed there was no correlation between the explosion and reports of North Korea preparing for a possible nuclear test.
The New York Times reported on Saturday that U.S. President George W. Bush and his top advisers recently received intelligence reports that could indicate North Korea is preparing its first nuclear test, citing senior officials with access to the intelligence.
John Irvine, a reporter for Britain's ITN TV who is in Pyongyang, said there has been no official response from the North Korean government, although there is pressure to provide an explanation.
"I'm touring outside Pyongyang, the North Korean capital, right now with the British Junior Foreign Minister Bill Rammell, who has just told me that he is demanding a response from the Ministry of Foreign Affairs here in North Korea," Irvine reported Sunday.
"[Rammell] does have a meeting with a senior foreign minister here tomorrow and Mr. Fammell anticipates some answers at least by then."
Yonhap reported the explosion happened in Yanggang province along the Chinese border, the site of Yongjori Missile Base -- a large facility with an underground missile firing range.
According to data gathered by Nuclear Threat Initiative (NTI), Yongjori is a suspected site for North Korea's uranium enrichment program.
According to its Web site, NTI is a private charity -- funded by CNN founder Ted Turner -- dedicated to lessen the threat posed by weapons of mass destruction -- nuclear, chemical and biological -- around the globe.
-- CNN National Security Correspondent David Ensor and Correspondent Sohn Jie-Ae contributed to this report