Authorities at a Moscow airport intercepted Tehran-bound luggage Friday containing 18 pieces of radioactive metal that can be used in nuclear operations. A U.S. intelligence official told NBC News that the materials were not likely tied to Iran's nuclear program—the metals can be used for medical diagnostics—but the official was still "deeply concerned" by the incident. This comes amid growing speculation that Iran is getting closer to creating atomic weapons in defiance of international agreements. Last month the UN Atomic Energy Agency reported that Iran was transporting enriched uranium to its nuclear facility in Qom, which prompted the UK and other western governments to tighten sanctions on the country. The U.S., this week, approved measures against Iran's Central Bank and are sending State Department officials to Israel to discuss "common security challenges," likely related to Iran's nuclear program, Bloomberg News reported.