Kathryn Cohen Allen facing nine counts of mailing hoax anthrax letters to Marco Rubio, Bill Nelson

Federal prosecutors say 45-year-old Kathryn Cohen Allen was arrested Tuesday in the Hamilton County town of Jasper. She had an initial court appearance in Jacksonville federal court but it was not immediately clear if she had an attorney.

A grand jury indictment accuses Allen of mailing threatening letters containing a non-hazardous white powdery substance in June 2011 to the two senators' offices. Allen is also charged with sending similar letters to government facilities in Hamilton County, the Florida Department of Children and Family Services and to three private citizens.

If convicted Allen could face up to 45 years in prison.