The International Atomic Energy Agency will conduct a second round of inspections at South Korea's nuclear facilities next week, government officials in Seoul said Wednesday.

The U.N. agency will begin new inspections Monday at South Korea's main nuclear lab in Taejon, 100 miles south of Seoul, focusing on 295 pounds of uranium metal, officials said.

The IAEA chief, Mohamed ElBaradei, who plans to visit South Korea in October, said Monday that the material had been produced at a previously undisclosed facility. Over the past two weeks, South Korea has admitted to enriching a small amount of uranium in 2000 and extracting plutonium in 1982 during scientific experiments that may have violated international laws.

IAEA investigators were in Seoul last week to collect samples, but European diplomats familiar with the investigation said they were seeking further information about the experiments, which they said showed enrichment to near bomb-grade levels. ElBaradei has described the tests as matters of "serious concern." South Korean officials have played down their importance, insisting that they amounted to simple research tests.

South Korea's intelligence agency, meanwhile, issued a rare statement lending credence to North Korea's claims this week that a massive explosion near its border with China on Sept. 9 was due to demolition work for a power-plant project.

The National Intelligence Service also said cloudy weather at the time may have made the explosion appear larger in satellite images.

The explosion could have been connected to the construction of a hydroelectric plant as North Korea asserted this week, the intelligence service said in a report to the National Assembly. The Pyongyang government has invited foreign diplomats to tour the site.

Secretary of State Colin L. Powell has told the Reuters news agency that North Korea's explanation was consistent with the U.S. assessment. Some analysts, however, have speculated that the blast was a military-related accident.