A five-member team from the International Atomic Energy Agencylaunched the inspection Monday at the state-run Korean Atomic Energy Research Institute in Daejeon, 160 kilometers (100 miles) south of Seoul.

On Thursday, two of the five inspectors returned to Seoul to visit another nuclear center in a northern part of the capital, Yonhap news agency said.

"I understand the IAEA inspectors are now documenting what they have obtained through the inspection and preparing to return to Vienna on Sunday as scheduled," an institute official said by phone from Daejeon.

"I think they have taken samples related with the past nuclear experiments," said the official who requested anonimity.

Earlier this month as a first team of IAEA inspectors was visiting South Korea, the government revealed that its scientists secretly enriched a small amount of uranium in 2000. Then came revelations that scientists had extracted a tiny amount of plutonium in 1982.

South Korea insisted the lab experiments were not linked to nuclear weapons programs. IAEA chief Mohamed ElBaradei, however, expressed "serious concern" about the activities.

The new inspection team would report back to the Vienna-based IAEA by November.

South Korea has made a fresh pledge that it would not develop or possess nuclear weapons, but would pursue research transparently.

The case, however, has already damaged multinational efforts to persuade Stalinist North Korea to give up its nuclear weapons programs.

Pyongyang has warned that it would not abandon its nuclear ambitions.

It also said North Korea would not attend multilateral talks on its nuclear program unless South Korea cleared up suspicions over its nuclear experiments.

South Korea said its scientists produced 150 kilograms (330 pounds) of uranium metal in 1982 in undeclared activities and a small amount of this was used in 2000 to produce a microscopic amount of enriched uranium.

The scientists also admitted to having extracted a miniscule amount of plutonium from 2.5 kilograms of fuel rods in secret research in 1982.

South Korea has the world's sixth-largest civilian nuclear industry, operating 19 power plants that produce 40 percent of the country's energy needs.

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