A Russian probe into the death of Palestinian leader Yasser Arafat has found that his death wasn't caused by radiation — a finding that comes after a French probe found traces of the radioactive isotope polonium and a Swiss investigation said the timeframe of his illness and death was consistent with that of polonium poisoning. Vladimir Uiba, the head of the Federal Medical and Biological Agency, said Thursday that Arafat died of natural causes and the agency had no plans to conduct further tests.