A package containing the poison ricin was intercepted by law enforcement this week. A preliminary investigation indicated it tested positive for ricin, a poison found naturally in castor beans, the official said. All mail coming into the White House is sorted and screened at an offsite facility before it ever reaches the White House. According to the Centers for Disease Control and Prevention, Ricin can be made from the waste material left over from processing castor beans. “If castor beans are chewed and swallowed, the released ricin can cause injury,” CDC officials said.