MOSCOW » Russia’s customs agency says it has seized radioactive metal from the luggage of a passenger bound for Tehran.

The Federal Customs Service said in a statement that its agents found 18 pieces of metal Friday at Moscow’s Sheremetyevo airport after a radiation alert went on. It says the gauges showed that normal radiation levels were exceeded by 20 times.

The customs agency said prosecutors have launched a probe into the incident.

The Interfax news agency says the pieces contained Sodium-22, a radioactive isotope of sodium that could only be produced at a nuclear reactor.

Sodium-22 is a positron-emitting isotope with a remarkably long half-life.