The missing material, Iridium-192, was reported to the International Atomic Energy Agency by Iran's nuclear regulatory body earlier this month, who warned neighboring Gulf States of its possible nefarious use.
A so-called dirty bomb, or radiological dispersion device, is a conventional weapon equipped with nuclear material. The idea behind a dirty bomb is to blast radioactive material, such as powder or pellets, into the area around an explosion.
Citing Saudi intelligence sources, Asharq al-Awsat reported Friday that the Iridium-192 was stolen as it was being transported from the Bushehr facility. The vehicle carrying the nuclear material was later found abandoned with its contents seized.
It remains unclear who stole the nuclear material and for what purpose.
The IAEA defines Iridium-192, a highly unstable isotope which emits both electrons and gamma-rays, as a category-2 radioactive substance. Substances with a category-2 classification can permanently injure or even kill a human being if exposed to the material within hours or days.
Iridium-192 is generally used for industrial reasons, utilized to locate flaws in metal components, despite the danger it poses to humans.
In July 2015, Iran and six world powers, namely Britain, China, France, Russia and the United States plus Germany, reached a nuclear deal over the country's controversial nuclear program.
The deal, which went into effect in January, requires Iran to scrap the bulk of its nuclear activities in return for the ease of international sanctions on the country's energy and financial sectors. It allows regular inspections of the facilities inside Iran.
Earlier this month, the UN nuclear watchdog said Iran must stop repeatedly overstepping a limit on its stock of a sensitive material set by the landmark deal with major powers.
The International Atomic Energy Agency (IAEA), which is policing the deal, said in a report in early November that Iran had slightly exceeded the 130-tonne soft limit on its stock of heavy water for a second time since the deal was put in place in January.