Preliminary tests indicate ricin was found in letters sent last weekend to New York City Mayor Bloomberg and the director of Mayors Against Illegal Guns. The American Postal Workers Union said the letters were postmarked in Shreveport, Louisiana.
"The letter obviously, referred to our anti-gun efforts but there's 12,000 people (who) are going to get killed this year with guns and 19,000 that are going to commit suicide with guns, and we're not going to walk away from those efforts," Bloomberg said.
There is no known cure for the toxic substance. A small amount can kill a person within 36 to 48 hours.
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