Russian authorities say they have seized radioactive material at a Moscow airport from the luggage of a passenger traveling to Iran.

The Customs Service issued a statement saying the radioactive isotope Sodium 22 was seized Friday at Moscow's Sheremetyevo International Airport several weeks ago from an Iranian citizen.

The agency said the discovery involved 18 pieces of radioactive metal that triggered airport sensors.

Officials said the isotope produced by particle accelerators can be used for medical or research purposes.

It was not immediately clear if there was any connection to Iran's controversial nuclear program, but officials say an investigation is underway.

The passenger's name was not disclosed.

Iran's ISNA news agency Friday quoted an official at the Iranian Embassy in Moscow as denying that radioactive materials were seized from the luggage of an Iranian passenger. He said that about a month ago, a misunderstanding arose in connection with a student who was carrying some materials for dentistry uses.

Russia built Iran's first nuclear power station and has delivered nuclear fuel for the reactor.

Western nations accuse Iran of pursuing nuclear technology in order to make nuclear weapons — a charge Tehran denies.