The United Nations confirmed Tuesday that its atomic investigators had found uranium enriched up to 83.7 percent in one of Iran’s underground nuclear facilities, but emphasized that the materials found were just “particles.” The International Atomic Energy Agency’s samples, taken during a Jan. 22 inspection at the Fordo nuclear facility, were perilously close to weapons-grade levels of purity, which is generally considered to be around 90 percent. Iran’s stockpile of enriched uranium has hovered around an accepted level of 60 percent for the past two years, according to the IAEA. Iran officials told the UN watchdog “that ‘unintended fluctuations in enrichment levels may have occurred,’” IAEA said, adding, “Discussions between the agency and Iran to clarify the matter are ongoing.” The spike marks the ninth consecutive quarter that Iran has enriched its nuclear materials close to the weapons-grade line, according to Bloomberg News. The IAEA censured the country twice in 2022 over the matter.