Kyrgyz officials last week caught two men trying to sell plutonium on the black market. Plutonium can be used to make nuclear weapons, but it can more easily be packed into dirty bombs, conventional explosives that can spew deadly radiation over a small area. Security officials in the former Soviet republic said the plutonium was likely smuggled from a neighboring country, such as Kazakhstan or Uzbekistan. When the Soviet Union fell apart, in 1991, the Soviet military abandoned stockpiles of decaying nuclear material all over Central Asia, and much of it is poorly guarded. Another Kyrgyz man was arrested earlier this year when he tried to sell cesium-137, another radioactive ingredient that could fuel a dirty bomb.