S. Korea: No Blast in N. Korea

South Korea (search) now believes that a mushroom cloud previously thought to be from a massive explosion in North Korea was actually a natural occurence and there was no blast, officials said Friday.

The mushroom-shaped cloud — initially detected by South Korean intelligence authorities and widely reported from an explosion — is believed to have been a natural cloud, said Deputy Unification Minister Lee Bong-jo during a weekly news briefing.

The size of the reported explosion and its timing on the 56th anniversary of North Korea's founding had raised speculation that it might have been a nuclear test. Experts said they don't believe the blast near the Chinese border was a nuclear test.

"We believe that there was no explosion in the place where intelligence authorities had previously suspected that there were signs of an explosion," Lee said.

However, North Korea acknowledged there was a massive explosion but said it took place in a different area as part of demolition work for a hydroelectric project. On Thursday, it allowed Britain's ambassador and other diplomats in Pyongyang (search) to visit the site of the Sept. 9 explosion to verify its claims that it wasn't caused by a nuclear test.

Lee said the site that North Korea opened to foreign diplomats was about 60 miles from the North's Kim Hyong Jik County, the site South Korean officials had initially pinpointed as a site for the mushroom cloud.