Shoffner, 68, was arrested at her home in Newport on Saturday by the FBI on extortion charges.
The agency said in federal court Monday morning that Shoffner's arrest followed a meeting at her home with a confidential informant who delivered a payment of $6,000 she had demanded.
If convicted, Shoffner faces not more than 20 years in prison and up to a $250,000 fine, or both followed by not more than 3 years supervised release.
Since her arrest, a number of officials, including Gov. Mike Beebe, Sen. Mark Pryor and Attorney General Dustin McDaniel had called for Shoffner to step down.
In a letter to Governor Mike Beebe, Shoffner wrote:
"It is with great sadness that I tender my resignation of the office of Treasurer of the State of Arkansas.
I am proud to have been elected by and to have served the people of the State of Arkansas and regret that I can no longer perform the duties and responsibilities owed to the public.
Please accept this resignation effective 5:00 p.m. today's date, May 21, 2013"
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