Moscow ( CNN ) -- Russian authorities on Friday seized radioactive material from the luggage of a passenger on a flight from Moscow to Tehran , Iran . The luggage , belonging to an Iranian citizen , contained 18 metal objects packed in individual steel cases , Russia 's Federal Customs Service said . The agency said the material , the radioactive isotope Sodium-22 , can be obtained in a nuclear reactor . The news sparked concern that the incident may have been related to Iran 's nuclear program , which the International Atomic Energy Agency said in a report last month could be geared to produce weapons . Iran has repeatedly said its nuclear program is solely for peaceful purposes . Nuclear expert Michael Friedlander said Sodium-22 has no applications related to weapons . It is generally used to calibrate nuclear instruments in medical equipment , he said . Initial tests showed that radiation levels of the objects were 20 times above normal , the Russian customs service said . Radiation expert Paddy Regan , a professor at England 's University of Surrey , said the material was unlikely to present a major hazard . He said Sodium-22 can be made in medical accelerators and is usually not produced in reactors . It is also not used in reactors as a component of fuel , he said . The customs agency said the objects were sent to a Moscow prosecutor 's office that deals with air and water transport . A criminal investigation is under way . No details were available on the identity of the Iranian passenger , who apparently flew to Tehran on the flight . Iranian news media quoted an embassy official in Moscow as saying any reports that the passenger had been arrested were false . `` These false allegations are meant to destroy relations between Iran and Russia , '' the official told the semi-official Iranian Students News Agency . `` A month ago there was a misunderstanding about a university student who was carrying material used in dentistry , '' he said . `` This misunderstanding was resolved quickly and the student received apologies . '' CNN 's Jo Shelley , Alla Eshchenko , Danielle Dellorto and Shirzad Bozorgmehr contributed to this report .
A nuclear expert says the material can not be used for research . Russian customs agency says the radioactive material can be obtained from a nuclear reactor . It was found in the luggage of a passenger on a flight to Tehran . Russia 's atomic expert says the material is used only for scientific research .