Paul Kevin Curtis Update: FBI says no ricin found in home of Mississippi suspect

(CBS/AP) OXFORD, Miss. - Investigators say they haven't found any ricin in the home of Mississippi man accused of mailing poisoned letters to President Barack Obama, a U.S. senator and a local judge.

PICTURES: Miss. man arrested in ricin letter case

FBI Agent Brandon Grant, testifying in federal court Monday, said a Friday search of Paul Kevin Curtis' house in Corinth, Miss., did not turn up ricin or ingredients for the poison. A search of Curtis' computers has found no evidence so far that he researched making ricin.

Federal investigators believed the letters were mailed by Curtis, an Elvis impersonator who family members say suffers from bipolar disorder.

Through his lawyer, Curtis has denied involvement in letters sent to Obama, Mississippi Republican Sen. Roger Wicker, and a Lee County, Miss., judge.

Curtis' lawyer suggested in court that an enemy may have framed Curtis.

Complete coverage of Paul Kevin Curtis on Crimesider