BEIJING (AP) _ A diplomat who visited the site of a huge explosion in North Korea said Friday he saw no evidence it was caused by a nuclear test, and South Korean officials said mushroom-shaped plume thought to be from the blast may have instead been a natural cloud formation.
The extremely secretive North allowed diplomats from seven countries to the site to prove its contention that the Sept. 9 blast was part of two planned detonations at a construction site for a dam in the country's remote northeast near the Chinese border.
Independent video of the site obtained by Associated Press Television News in the North Korean capital of Pyongyang, hours after the ambassadors returned from their visit, showed a construction site consistent with a large dam project.
``One thing is entirely clear: This was not a nuclear explosion that happened at this site,'' Swedish Ambassador Paul Beijer, who was among the visiting delegation, said by phone from Pyongyang. ``This is a site where thousands of people are working on dam building.''
Concern was sparked when South Korea reported days after the blast that a mushroom cloud more than two miles across was seen on satellite.
But on Friday, the South's deputy unification minister, Lee Bong-jo, said the cloud may have been a natural formation and unconnected to the construction blasts.
Lee said the site that North Korea opened to foreign diplomats was about 60 miles from the site South Korean officials had initially pinpointed as a site for the mushroom cloud.
``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 at a news briefing.
The size of the cloud seen on satellite photos and its timing on the 56th anniversary of North Korea's founding led to speculation that it might be a test by the North's nuclear program. Experts say they don't believe North Korea would have conducted such a test near the Chinese border.
The incident occurred during efforts to arrange a new round of six-nation talks on Washington's demand for the North to give up its nuclear development. The talks also include host China, Russia, South Korea and Japan.
British Foreign Office Minister Bill Rammell said this week that North Korea's foreign minister told him during a visit to Pyongyang that there was a blast as part of demolition work for a hydroelectric project _ but no nuclear test.
In the video obtained by APTN, a North Korean official was seen pointing out a big billboard illustrating the completed project.
The video, apparently shot from a point high above the valley floor, showed a building complex intact near a place where rock had been blasted away. Scores of workers swarmed around the site.
A deep excavation could be seen across the valley, apparently where the dam is intended to rise.
Beijer said North Korean officials at the construction site told the diplomats the blasts were unusually large and needed for construction of the dam. He said they explained how much explosive was used.
The delegation was led by Britain's ambassador to North Korea, David Slinn, and also included diplomats from Russia, Poland, Mongolia, Germany, Sweden and the Czech Republic. The Swedish ambassador did not say whether delegates carried Geiger counters or took soil samples at the site.
Slinn declined to comment, but the British Foreign Office issued a statement in London saying the group had visited the construction site of a hydroelectric project.
The diplomats reached the site in Samsu County after a 1 1/2-hour flight and then a three-hour drive by off-road vehicle, Beijer said. They spent about 90 minutes taking photos, talking to officials at the site and gathering information that their governments' technical experts would analyze, he added.