German prosecutors said Friday they have dropped an investigation of a Russian businessman who had been suspected of transporting a radioactive substance used in the fatal poisoning of a former Russian agent in London in 2006.
Alexander Litvinenko _ a former Russian security agent who became a fierce Kremlin critic and was granted asylum in Britain _ died in November 2006 of what doctors said was poisoning with polonium-210, a rare radioactive isotope.
Hamburg prosecutors started investigating Russian businessman Dmitry Kovtun at the end of that year on suspicion that he may have illegally handled radioactive material.
They closed their investigation on Nov. 6 after concluding there wasn't enough evidence to charge Kovtun, spokesman Wilhelm Moellers said.
Kovtun was hospitalized for suspected radiation poisoning in December 2006. German authorities said they found traces of polonium-210 in locations in Hamburg visited by Kovtun just before he traveled to London, where he met with Litvinenko.
Kovtun has denied having anything to do with the substance. The German investigation focused solely on whether he handled the material and did not address Litvinenko's death itself.
British prosecutors have named a former KGB officer, Andrei Lugovoi, as their chief suspect in Litvinenko's poisoning, but Russia has refused to hand him over and the case has strained British-Russian ties. Lugovoi has denied involvement in the death.
Before his death, Litvinenko recorded a searing message from his hospital bed blaming Russian authorities, including then-President Vladimir Putin, for his killing.