There's been an arrest by federal authorities who are trying to track down the person responsible for last month mailing possibly ricin-laced letters to President Obama, New York City Mayor Michael Bloomberg and a gun control group the mayor supports.

Local news outlets say the person arrested is not the New Boston, Texas, man who authorities initially identified as a "person of interest."

Instead, it's the man's wife. And it could be that the motivation behind the letters had nothing to do with Bloomberg's or Obama's efforts to tighten the nation's gun laws.

KTBS-TV in Shreveport, La., reports that:

"Shannon Richardson has been arrested. ... Shannon's husband, Nathan Richardson, was named as a person of interest after Shannon contacted authorities about a suspicious substance she found in their refrigerator. Nathan Richardson was questioned by the FBI last week and released. ... Attorney John Delk says his client, Nathan Richardson, approached him [last year] about getting a divorce. ... 'We have very good reason to believe it was a setup,' said Delk."

NBC News' Pete Williams says Shannon Richardson "was arrested in Arkansas on charges that will be filed Friday afternoon, the authorities said."

Shreveport's KSLA-TV adds that "Shannon Richardson was seen going into the federal courthouse in downtown Texarkana just before noon, accompanied by federal agents."

If authorities do prove that Shannon Richardson sent the letters and then pointed authorities to her husband, this could be the second case in the past two months in which someone was allegedly framed for mailing the deadly poison to Obama and other officials.

In April, Pual Kevin Curtis of Mississippi was initially suspected of sending such letters to the president, a senator and a local judge. But authorities soon zeroed in on another Mississippi man, James Everett Dutschke, who reportedly had run-ins with Curtis in the past. Dutschke has since been indicted on five federal charges, from sending threats in the mail to knowingly making and possessing "a biological agent... for use as a weapon."

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