Senior U.S. officials say they are deeply concerned by reports of the seizure of smuggled radioactive material heading into Tehran and commend the Russian security services for seizing the material.
That said, an early read by U.S. intelligence is that the main purpose of this isotope, Sodium-22, is for medical diagnostics. It's used for radiation therapy -- and officials say the materials can be bought legally, so it does not have implications for suspected weapons development.
"We don't know whether the receipient was a government agency," one agency said. "It's unclear why they would want to smuggle it in; we are still investigating, but it does not appear that this involves Iran's nuclear program."