A day after twin bombings rocked Boston, a senior Republican Senator received a letter tested positive for the deadly poison ricin, prompting the FBI to launch a probe.


The envelope addressed to Roger Wicker was tested positive for ricin, a highly poisonous substance, Senate Majority Leader Harry Reid said. Following this, the authorities have increased security for the Mississippi Senator.


An FBI official said tests on the substance was undergoing further analysis at a laboratory. Missouri Senator Claire McCaskill said authorities have identified a suspect who may have sent the letter. "The person that is a suspect writes a lot of letters to members," McCaskill was quoted as saying by media reports.


The letter's discovery came a day after the twin Boston bombing that left three people dead and more than 170 injured. According to the Centers for Disease Control and Prevention, ricin is a poison found in castor beans, which can be manufactured from castor bean waste materials.