Story highlights I didn't even know what ricin is, cleared suspect tells CNN

On Tuesday, authorities dropped charges against Paul Kevin Curtis

FBI agents searched a former martial arts studio on Wednesday, lawyer says

The studio's former operator denies involvement through his attorney

FBI agents on Wednesday searched the former martial arts studio of a Tupelo man in connection with the investigation into ricin-tainted letters sent to President Barack Obama and other officials, the man's lawyer, Lori Basham, told CNN.

Agents in hazardous materials suits had searched James Everett Dutschke's home on Tuesday, the same day prosecutors dropped charges against the man arrested last week on suspicion of sending the letters.

Authorities have not called Dutschke a suspect and no charges have been filed. It was unclear what, if anything, they found.

Basham said Dutschke has not yet spoken to federal investigators. He did sign a consent form allowing the searches, she said. Dutschke no longer rents the taekwondo studio space, she said.

Investigators are trying to determine whether someone attempted to pin the poisonous letters on Paul Kevin Curtis of Corinth, Mississippi, a law enforcement source told CNN Tuesday on the condition of anonymity.

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However, Curtis' attorney, Christi McCoy, said Wednesday on CNN that she believes investigators are now focusing on the possibility that the letters were a direct attack on the politicians they were addressed to, not purely an attempt to get at Curtis.

"Kevin just happens to be the scapegoat for it," she said.

In a court hearing Monday before the charges were dropped, Curtis said he was being framed and identified Dutschke as a potential culprit. Basham said Wednesday her client had nothing to do with the letters.

Prosecutors initially arrested Curtis April 17 and charged him with sending a threat to the president after letters containing a suspicious powder triggered security scares around Washington.

The letters -- sent to Obama; Sen. Roger Wicker, R-Mississippi; and Sadie Holland, a judge in Lee County, Mississippi -- touched off anxieties in Washington and elsewhere in the wake of the bombing of the Boston Marathon. The two incidents were unconnected, officials said.

The FBI said the letters tested positive for ricin, a toxin derived from castor beans that has no known antidote. No illnesses have been reported.

Authorities dropped the charges against Curtis on Tuesday after new information became available, U.S. Attorney Felicia Adams said.

McCoy said Wednesday that she does not believe Curtis is under any remaining suspicion. She said she believed investigators identified her client from constituent records maintained by Wicker's office and concluded he was responsible based on thin evidence.

She believes Curtis had been framed by someone who used several phrases he likes to use on social media.

The letters read, in part: "To see a wrong and not expose it, is to become a silent partner to its continuance."

They were signed "I am KC and I approve this message," a source told CNN.

Each letter had a Memphis, Tennessee, postmark and no return address.

Basham said Dutschke used to work for Curtis' brother, but the two have had no contact since 2010.

Curtis said Wednesday that he didn't even know what ricin is until he got out of jail and looked it up on the Internet.

When police suddenly stormed his home last week, Curtis said an investigator asked him about ricin, and Curtis said he responded, "Well, I don't eat rice, and I don't have any rice in the house."

While investigators didn't initially accept his claims of innocence, and he came close to losing hope during his week in jail, he said it's turned out as well as he could have hoped.

"This has restored my faith in our justice system," he said Wednesday on CNN.