REPORTS: Man Arrested In Connection With Poisonous Mailings Sent To Obama And US Senator

Daniel Goodman / Business InsiderPolice have made an arrest in a case involving various letters sent to federal officials, including President Barack Obama, that contained the deadly poison ricin.

NBC News and The Clarion Ledger are both reporting that Paul Kevin Curtis of Tupelo, Miss., has been arrested in connection with letters addressed to Sen. Roger Wicker (R-Miss.) and Obama.

The Ledger reported that Curtis signed both letters "I am KC and I approve this message."

"To see a wrong and not expose it, is to become a silent partner to its continuance," he wrote.

Earlier in the day, White House press secretary Jay Carney said that the FBI had a "lead" in the investigation.

According to the Centers for Disease Control and Prevention, ricin is a poison naturally found in castor beans. It gets inside the cells of a person's body, preventing the cells from making any proteins. It can come in the forms of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid.

A ricin scare in 2004 temporarily shut down three Senate offices. Postal workers began sorting through an off-site after the 2001 anthrax attacks that targeted, among others, then-Majority Leader Tom Daschle and Vermont Sen. Patrick Leahy.