A third team of U.N. nuclear inspectors will visit South Korea this week to examine the country’s past undeclared nuclear activities.

An official of South Korea’s Science and Technology Ministry says the visiting team was believed to be last to be dispatched by the International Atomic Energy Agency or IAEA.

South Korea has been scrutinized by the U.N. nuclear watchdog since it acknowledged in early September that its scientists had extracted or enriched small amounts of plutonium and uranium in 1982 and 2000 in violation of international treaties, but apparently without reporting it to the government.

IAEA inspection teams have visited South Korea on two occasions in early and late September to verify Seoul’s claims on the issue.

South Korean officials said the investigation will lead to a final report to be submitted to the IAEA Board of Governors, which will hold a meeting late next month.

If the investigation results are found to be serious enough, the board has the authority to refer the South Korean case to the U.N. Security Council.