Iran said Thursday that talks with the UN nuclear watchdog on investigating traces of weapons-grade uranium that were found at a university in Teheran were constructive, state media reported. "Technical talks about the source of contamination were held in a constructive atmosphere," Ali Asghar Soltanieh, the country's envoy to the UN agency, was quoted by the official IRNA news agency as saying. "Another step was taken in the direction of settling the remaining problems surrounding Iran's nuclear issue." Soltanieh, who headed the 3-member Iranian team in the talks, said Iran "answered and explained" all questions from the International Atomic Energy Agency. It is not clear how or when the find of the uranium traces was made.