Preliminary tests on a letter sent to U.S. President Barack Obama indicate the presence of suspicious substance, the Federal Bureau of Investigation (FBI) said Wednesday. The letter was undergoing further testing because preliminary field tests can be unreliable, creating false positives. The letter was intercepted at screening facility separate from the White House. It came the day after officials said a letter sent to Senator Roger Wicker tested positive for ricin. That letter to Wicker was intercepted at a Senate mail facility just outside Washington.
