The United Nations' International Atomic Energy Agency (IAEA) reportedly found "new evidence of undeclared nuclear activities" at two sites in Iran. If true, that would constitute a violation of the nation's international obligations.
The IAEA took samples from the two sites which "contained traces of radioactive material" and "could indicate Iran has undertaken work on nuclear weapons, based on where it was found," according to a Wall Street Journal report.
Iran blocked the IAEA from investigating the two sites last year. Iran also reportedly threatened to restrict the inspectors' ability to access sites in the coming weeks.