Skepticism over N. Korean blast
 |  File picture of the region where the blast is believed to have gone off. |
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|  VIDEO |
 North Korea says cloud was the result of a deliberate demolition
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WASHINGTON (CNN) -- U.S. and South Korean officials are still trying to verify what triggered a massive mushroom cloud in North Korea amid skepticism over Pyongyang's explanation of the event.
After several days of speculation, North Korea said on Monday the 4-kilometer (2 miles) wide cloud spotted on satellite images by South Korea's Yonhap agency was the result of a deliberate demolition of a mountain for a power plant.
North Korean Foreign Minister Paek Nam Sun provided the explanation to British Foreign Office Minister Bill Rammell, who has just concluded a four-day visit to the reclusive nation.
Rammell said Tuesday he also formed the view that North Korea was committed to holding six-party talks aimed at resolving the crisis over its nuclear weapons program. But he said Pyongyang was not yet prepared to commit to a date. (Full story)
The cause of the smoke, which was spotted on the day North Korea marks its founding, is still a mystery to U.S. and South Korean intelligence, though the Communist state is watched closely using spy satellites and other means.
A Bush official said Monday the administration is not prepared to "speculate" about what happened in North Korea.
The administration is not saying it thinks the blast was part of a demolition project, as the British Foreign Office does. One American official said: "That could be true, but we don't know. We can't rule it out."
The U.S. does not think it was a nuclear event, but an administration official cautioned: "We still don't know what it was, and we're not speculating."
U.S. officials say they are still reviewing satellite imagery and other intelligence on the matter.
Some outside analysts have speculated the explosion could have been at the Yongjo-ri Missile Base, a facility believed to house up to 36 NoDong missiles. U.S. officials say there is no evidence that is true, though it cannot be completely ruled out.
According to data gathered by the Nuclear Threat Initiative (NTI), Yongjo-ri is a suspected site for North Korea's uranium enrichment program.
South Korea skeptical too
On Tuesday South Korea's defense minister said the country was seeking independent verification on the nature of the blast.
Yoon Kwang-woong said the South would use intelligence channels and satellite images to check on the source of the blast in a northern region of the North.
"The weather is clear, so we should be able to take satellite images today and tomorrow and analyze them," Yoon told pool reporters ahead of a cabinet meeting on Tuesday.
"We should be able to confirm the site of the explosion."
Hydroelectric experts in Seoul have questioned the North's explanation, saying the relatively small Huchang river in the area made it an unlikely and unfeasible site for a major hydro power plant, according to Reuters reports.
The nation's media have also raised questions, with the Chosun Ilbo newspaper quoting a North Korean defector familiar with the region who said the body of water in the area was not sufficient for a large power plant.
Britain's Foreign Office has said North Korea is allowing international diplomats to inspect the site.
North Korea's vice foreign minister for Europe, Kung Sok Ung, said Britain's ambassador to Pyongyang, David Slinn, could go to the site as soon as Tuesday.
North Korea's official KCNA news agency said late Monday that reports of a large accidental explosion at the site or a nuclear test was a "preposterous smear campaign."
"Probably, plot-breeders might tell such a sheer lie, taken aback by blastings at construction sites of hydropower stations in the north of Korea," KCNA said.
CNN Radio, CNN National Security Correspondent David Ensor and Correspondent Sohn Jie-Ae contributed to this report.
