S. Korea, U.S. Say Mass Explosion Likely Not Nuclear Test

SEOUL, Sept. 12 -- South Korean officials said on Sunday that a massive explosion generating a huge cloud of smoke on North Korea's northern border with China on Sept. 9 was an unspecified accident and apparently not a much-feared nuclear test.

"We are investigating the size and the reason of the accident but we do not believe North Korea conducted a nuclear test," Kim Jong Min, South Korean presidential spokesman said Sunday.

Details of the blast, which came as concerns were mounting in U.S. intelligence circles in recent weeks that North Korea was about to conduct a nuclear test, remained sketchy. But South Korean officials said they recorded none of the seismic activity that likely would have accompanied a nuclear test.

Secretary of State Colin L. Powell, echoing that assessment, said the explosion Thursday was not a nuclear test but that it was not known yet what caused it.

"There was no indication that was a nuclear event of any kind. Exactly what it was, we're not sure," Powell said on ABC's "This Week."

China's government, which has the closest relations with North Korea, had no immediate comment about the reported explosion.

Nevertheless, the date of the blast -- on a day commemorating the 1948 founding of North Korea -- had U.S., South Korea and Japanese officials scrambling to analyze satellite images for a clearer picture of what may have caused the huge explosion. North Korea is known to put great importance on historic dates, using such occasions to conduct high-profile military exercises and parades.

One official in Washington said the Americans were examining satellite images of the explosion -- which South Korea's semi-official Yonhap news service said generated a mushroom cloud formation as large as 2.5 miles in diameter -- and that further information had been provided to the U.S. government by a diplomatic source in Beijing.

However, the official said the explosion did not take place at the location that had been closely monitored in recent weeks by U.S. intelligence agencies. Suspicious movement of vehicles at that location led some analysts to believe preparations for a nuclear test might be underway.

The explosion -- reportedly larger than a chemical blast near a train station in North Korea last April that killed 150 persons -- took place in North Korea's Kim Hyong Jik county inside the northern Yanggang Province near its mountainous border with China, South Korean officials said. In 1999, a South Korean presidential spokesman told The Washington Post that the Pyongyang government was building an underground ballistic missile launching facility in that region for the Taepodong-1 -- a missile that North Korea test-fired over Japan in 1998 -- and the longer-range Taepodong-2, which is believed to be in the final stages of development. Since then, some analysts have suspected that the heavily militarized, remote area may also house a new, intermediate North Korean missile with a range of between 1,800 and 2,500 miles and may additionally be a facility used for uranium reprocessing.

In December 2002, a missile engine test is believed to have caused an explosion that destroyed facilities at North Korea's launching pad in Musudanri, North Hamkyong Province -- though it was quickly rebuilt for a successful test of the Taepodong-2's main engine in May, intelligence officials now believe.

Given the missile facilities in the area of last week's explosion, a South Korean official, who spoke on the condition he not be named, said one working theory for the explosion was a possible missile-related accident. But the official stressed that intelligence on the explosion was still too vague to provide a conclusive cause.

The location of the blast also led some analysts to discount a nuclear test, given that it took place so close to North Korea's border with its closest ally, China.

"North Korea would not have tested any nuclear material close to China," said Koh Yu Hwan, professor of North Korean studies at Seoul's Dong Guk University. "It would contaminate a huge area, including Chinese soil. North Korea won't take that risk."

European diplomats reached in Pyongyang said there had been no briefing or explanation offered to them in the North Korean capital. In April, when train wagons carrying chemicals to a railway station exploded in the North Korean town of Ryongchon, killing 150 people and injuring an estimated 1,300, the Pyongyang government made a surprising break with its habit of remaining mum on disasters. But this time, North Korea remained predictably silent.

"That is not a place that is open to access for us," said one European diplomat by phone from Pyongyang, referring to northern Yanggang province. "There has been no official announcement here."

The April 22 explosion in North Korea produced a perimeter more than a mile wide. The blast was believed to have been sparked by a train laden with oil and chemicals that hit power lines.

An unnamed source in Beijing told Yonhap on Sunday that last week's blast in North Korea was bigger than the train explosion in Ryongchon.

Staff Writer Glenn Kessler contributed to this report from Washington. Special correspondent Akiko Yamamoto contributed to this report from Tokyo.