Authorities were observed searching a home in New Boston, Texas, Thursday in video shot by Shreveport, La., television station KSLA, CBS News said Friday.
The FBI questioned the person in Texarkana, Texas, the report said.
The Secret Service said a possible ricin-tainted letter sent to Obama Thursday bore similarities to a letter sent to Bloomberg.
A spokeswoman with the FBI's Washington Field Office said the Secret Service intercepted a "suspicious letter" and the FBI was testing it for the highly toxic material, The Washington Post reported.
"U.S. Secret Service can confirm that the White House mail-screening facility intercepted a letter addressed to the White House that [was] similar to letters previously addressed to Mayor Bloomberg in New York," the Secret Service said in a statement. "This letter has been turned over to the FBI Joint Terrorism Task Force for testing and investigation."
On Wednesday, authorities intercepted ricin-contaminated letters mailed to Bloomberg and the gun-control group he founded, Mayors Against Illegal Guns, which has been an outspoken advocate in the recent push for stricter gun laws.
Earlier this year, ricin-laced letters were sent to Obama, Sen. Roger Wicker, R-Miss., and a Mississippi judge. Police in Washington state last week arrested a man in an inverstigation into a death threat to a judge and two ricin-tainted letters sent earlier this month.