BANGOR, Maine — Suzanne Muscara, 37, of Burlington, Maine pleaded not guilty in federal court on Thursday.

Muscara was arrested and charged earlier this month after sending a letter that she claimed contained ricin to Sen. Susan Collins' Bangor home.

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Muscara was officially charged with mailing a threatening communication to a U.S. government official protected under federal law.

Muscara will stand trial in June. If convicted, she faces up to 10 years in prison and a $250,000 fine.