51.   The latter two are highly radioactive substances used in medical applications.

52.   The man arrested in Switzerland has been released on bail, but still faces charges for violating Swiss law on radioactive substances, it said.

53.   The origin of the highly radioactive substance, apparently smuggled to Macedonia, was not revealed.

54.   The Pakistani officials would not say whether Padilla was successful in obtaining radioactive substances, nor would they identify the country he was said to have visited.

55.   The rods were bathed in the liquid acid, which extracted uranium, plutonium and other radioactive substances but left behind a highly radioactive stew of other metals.

56.   Thefts of radioactive substances have been on the rise in Russia, as lax security at many industrial plants allowed workers to steal and sell them.

57.   The United States has said that security of Russian nuclear facilities is not tight and has raised concerns that terrorists could try to acquire radioactive substances from Russian sources.

58.   The United States also is troubled by the porous borders allowing alleged terrorists to transport weapons and money and smugglers to spirit out radioactive substances.

59.   There have been numerous cases involving the theft or sale of radioactive substances.

60.   The weapon would have apparently involved packing radioactive substances into conventional bombs or missiles.