Paek Nam-sun, officially stated that the explosion "was in fact the deliberate demolition of a mountain as part of a huge hydroelectric project". North Korea announced on 13 September 2004 that the British ambassador, David Slinn, would be permitted to visit the site. Diplomats from the United Kingdom, Sweden, Germany, the Czech Republic, Poland, Russia and Mongolia visited what was purported to be the site on 16 September 2004, and reported having seen a hydroelectric project under construction. However, South Korea said the diplomats had not been in the correct location and were about 100 km (62 mi) from the suspected explosion site. From South Korea On 17 September 2004, South Korean Vice Minister of Unification Rhee Bong-jo claimed that there was no explosion at all at the purported site, saying the supposed mushroom cloud was a natural cloud formation (mushroom clouds form from many types of large explosions, not only nuclear detonations). On the same day, the Korea Earthquake Research Center reported that the only seismic activity in Ryanggang province in the period in question was at 23:24 Korea Standard Time (UTC +9) on 8 September 2004 at Mount Baekdu, about 100 km from the suspected blast site. North Korean disarmament talks At the time of the blast, North Korea was under pressure to again resume six-way diplomatic talks concerning its nuclear program with the United States, South Korea, the People's Republic of China, Russia, and Japan. North Korea was insisting on a delay before a fourth round of talks, citing recently revealed South Korean nuclear research programs. On 14 September 2004, a British envoy said that North Korea was still committed to the talks, but on 27 September 2004, the KCNA, North Korea's state news agency, reported that resumption of the talks was out of the question until the United States made certain concessions. Since the initial days, there has been essentially no follow-up reporting in Western media. On 28 September, North Korean Vice Foreign Minister Choi Su-heon announced at the United Nations General Assembly that it had turned plutonium from 8,000 spent fuel rods into nuclear weapons as a deterrent against the US nuclear threat. Six-nation talks on the nuclear issue, which were due to resume, were instead suspended. As of this date, analysts believed North Korea had ruled out further talks until after the United States presidential election in November 2008. Since then, North Korea has