Sen. Susan Collins, R-Maine, arrives in the Senate on Capitol Hill in Washington, March 14, 2019. Credit: J. Scott Applewhite | AP

The Burlington woman accused of sending a threatening letter to U.S. Sen. Susan Collins’ Bangor home last fall pleaded not guilty Thursday to one count of mailing threatening communications.

Suzanne E.Muscara, 37, is being held without bail.

Her trial was tentatively set for June in U.S. District Court in Bangor.

Muscara allegedly mailed a letter to the Republican senator in October that contained a white powder the sender claimed was anthrax. The letter came after Collins’ vote to confirm Brett Kavanaugh to the U.S. Supreme Court.

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The letter was addressed to Collins at her current Bangor home. The return address on the envelope was for Collins’ prior residence. The letter was intercepted at the U.S. Postal Service’s sorting facility in Hampden on Oct. 17, two days after Collins’ husband received a similar letter in the mail at the couple’s Bangor home.

No one has been charged in connection with that mailing, according to the U.S. attorney’s office.

The second letter contained an Aetna Medicare Solutions colored flyer, according to a court affidavit. On one side in blue handwriting was written, “AnthRAX!!! HA HA HA!!!”

“A stick-figure face has been drawn with the letter ‘X’ for eyes, the tongue sticking out, and with ‘You’ and an arrow pointing at the stick figure face,” the affidavit said.

The FBI was able to obtain a partial fingerprint from the second envelope after determining the powder was starch. The fingerprint was matched to Muscara, whose fingerprints had been collected following a 2013 arrest in Pennsylvania, the affidavit said. The circumstances surrounding that arrest were not included in court documents.

Recently unsealed search warrants for Muscara’s car and home revealed more information about the Green Party member.

She bought some land and moved to Burlington — a Penobscot County town of fewer than 400 people located southeast of Lincoln — in December 2013, according to court documents. She lived on Sibley Road in a trailer until late 2017 when it was destroyed in a fire that injured Muscara.

The person from whom Muscara purchased the land allegedly told an investigator that Muscara went to stay with relatives in New Jersey while she recovered. She returned in April or May 2018 and arranged to rent a cabin on Twin Hills Road owned by the same person from whom she bought the land.

The land owner, who is not identified in court documents, said that Muscara left in December or January and said she’d return in April to collect her things because she was going to move in with her family in New Jersey.

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Investigators learned that Muscara appeared to be living in her car in southern states in January, February and March, the affidavit said. Out-of-state police allegedly had contact with Muscara on Jan. 12 in Gulf Shores State Park in Alabama, on Feb. 11 in Mississippi and on March 10 in Knoxville, Tennessee.

She returned to the cabin in Burlington on April 1 and was arrested on April 5. Muscara allegedly confessed to sending the letter but told investigators she never expected the letter would be delivered or taken seriously.

Police did not seize any items from her cabin but took a laptop, an envelope with handwriting on it, a notebook with handwriting in it, a cell phone, an expired passport and other items from her car, according to court documents. The handwriting on the letter sent to Collins is expected to be compared to the handwriting on the items taken from Muscara’s car.

If convicted, Muscara faces up to 10 years in federal prison and a fine of up to $250,000.