J. Everett Dutschke came out of his home and confirmed an FBI team was at the home and had questioned him, the Tupelo Daily Journal reported. Dutschke said he had nothing to do with ricin.
The newspaper said several law enforcement units were at the home, including Mississippi's full-time emergency terror response team.
Kevin Curtis attorney Christi McCoy told prosecutors to take a look at Dutschke, saying he had a heated email exchange with her client in 2010.
Meanwhile, officials in Oxford, Miss., confirmed Curtis has been released from custody. Curtis had been accused of mailing ricin-laced letters to President Obama and Sen. Roger Wicker, R-Miss.
"I respect President Obama," Curtis told reporters after his release. "I love my country and would never do anything to pose a threat to him or any other U.S. official.
"This past week has been a nightmare for myself and my family. ... I would like to get back to normal."
A relative of Curtis said investigators found a fingerprint on one of the letters, evidence that suggests someone other than Curtis sent the letters, WREG-TV, Memphis, reported Tuesday.
"That fingerprint does not belong to my brother Kevin Curtis," Jack Curtis said.
Jeff Woodfin, Oxford's chief deputy marshal, confirmed Curtis was no longer in custody but said he did not know the circumstances of the release.
After a Monday hearing in Oxford, in which the FBI said no traces of ricin could be found in Curtis' home, a Tuesday hearing was canceled, CNN said.
Curtis was then released from custody, a U.S. Marshal's Service spokesman said.
Ricin is a highly toxin natural substance from the castor plant.
There has been another ricin incident, this one at Bolling Air Force Base in southeast Washington, the top U.S. Senate Democrat said Tuesday.
Senate Majority Leader Harry Reid of Nevada told reporters: "We've had another incident today I'm told at Bolling Air Force base. Same substance." Reid told a press availability in Washington he could release no other details.