Letter to US senator tests positive for poison

           
An envelope addressed to a Republican senator twice tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.                         

One senator, Claire McCaskill of Missouri, said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added the letter was sent from an individual who frequently writes lawmakers.                       

Late Tuesday, Sen. Roger Wicker of Mississippi released a statement acknowledging the letter and said it was sent to his Washington office.                         

"This matter is part of an ongoing investigation by the United States Capitol Police and FBI," Wicker said. "I want to thank our law enforcement officials for their hard work and diligence in keeping those of us who work in the Capitol complex safe."                           

On Tuesday night, FBI spokesman Paul Bresson said initial field tests on the substance produced mixed results and that it is in the process of undergoing further analysis at an accredited laboratory. Only after that testing can a determination be made about whether the substance is ricin, Bresson said.


AP