An Associated Press investigation reveals that a remote corner of eastern Europe has become a thriving marketplace for nuclear material aimed at extremists in the Middle East. Here are five key findings:

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— Criminal gangs with Russian ties have made repeated attempts in recent years to shop bomb-grade nuclear material in Moldova to Middle Eastern buyers.

— Early this year, a gang specifically sought a buyer from the Islamic State group for highly radioactive cesium. The AP has exclusive details of the previously unpublicized case.

— In 2011, an organized crime ring led by a shadowy Russian nicknamed "the Colonel" tried to sell bomb-grade uranium to a real Middle Eastern buyer, in the most serious of four cases in the past five years.

— Hatred for the United States motivated the middleman in the 2011 case. In his home, police found diagrams on how to make a dirty bomb and a weapons contract made out to the ring's target buyer.

— The nuclear smugglers are getting off lightly with short prison sentences and resurfacing repeatedly to return to the illicit trade — showing that the trafficking is not under control.