A senate official has said that a laboratory test confirmed a letter to the Senator contained poisonous ricin, according to the Associated Press. More tests are expected, the official added.
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The announcement marks the end of a four-and-a-half year campaign by an array of forces against the extremist group.
The top temperature will be around 14 Celsius (57F).
Officers carried out first aid and paramedics were called to the scene, but the victim was pronounced dead a short time later.