RICIN ARREST: Miss. Man Suspected of Sending Letters to President and Senator

A Tupelo, Mississippi, man suspected of mailing letters laced with the poison ricin to President Obama and a U.S. senator was arrested by federal agents on Wednesday.

He was identified as Kenneth Curtis of Tupelo, Mississippi, and allegedly signed the letters: "I am KC and I approve of this message." Both letters had an April 8th postmark and included the phrase, "to see a wrong and not expose it, is to become a silent partner to its continuance."

Ricin, which is made from castor beans, can kill within 36 hours if ingested or inhaled and there is no known antidote.

Although initial tests on the letters showed some ricin, they were inconclusive, so further testing was ordered.