"Today at approximately 5:15 p.m. (2215 GMT), FBI special agents arrested Paul Kevin Curtis, the individual believed to be responsible for the mailings of the three letters sent through the US Postal Service," the Justice Department said.
The letters "contained a granular substance that preliminarily tested positive for ricin," it added in a statement.
Earlier reports had said that the letters to Obama and Republican Senator Roger Wicker of Mississippi were signed, "I am KC and I approve this message."
Curtis was arrested at his home in Corinth, Mississippi, the Justice Department statement said.
Ricin -- a highly toxic protein found in castor beans -- can, when inhaled, cause respiratory problems. Ingested orally, it is lethal in even miniscule quantities.
source: interaksyon.com
