In late 2006, "New traces of plutonium and enriched uranium– potential material for atomic warheads– have been found the IAEA in a nuclear waste facility in Iran." However, "A senior U.N. official who was familiar with the report cautioned against reading too much into the findings of traces of highly enriched uranium and plutonium, saying Iran had explained both and they could plausibly be classified as byproducts of peaceful nuclear activities." In 2007 these traces were determined to have come from leaking used highly enriched uranium fuel from the Tehran Research Reactor, which the U.S. supplied to Iran in 1967, and the matter was closed.