Russia has seized a consignment of radioactive isotope from a Iranian passenger at an airport in Moscow.
The man, who was to travel on a flight to Tehran, triggered a radiation alert at the airport.
Customs said on Friday that the the Sodium-22 could have been obtained only as the result of the work of a nuclear reactor.
Customs was alerted by a warning system at Sheremetyevo airport that background radiation in the departures hall was 20 times the norm. A passenger's bag was then searched.
Eighteen metallic objects of industrial origin were found, packed in individual steel boxes. No further details were issued.