WASHINGTON — Federal officials unsealed charges Tuesday against an Oklahoma man accused of mailing hundreds of letters containing suspicious substances to members of Congress and other officials last month and ahead of the 2024 election.

The court records, unsealed in the U.S. District Court for the Western District of Oklahoma, show officials filed a complaint against Robin Martin with two charges: conveying false or misleading information and hoaxes and mailing threatening communications. Martin is set to make his first court appearance Tuesday; information for an attorney was not immediately available.

The complaint alleges Martin sent more than 700 letters to election officials across the country as well as letters to members of Congress of both parties containing suspicious substances. The substances have so far tested as nontoxic and are believed to be yeast or flour, the complaint says.

The complaint alleges that Martin started sending letters with suspicious substances ahead of the 2024 election, addressing them to election officials in all 50 states. Some of those letters had messages written on them that could only be shown by exposure to ultraviolet light, the complaint says.

The mailings contained letters that claimed President Donald Trump won the 2020 election and raised concerns about issues with the 2024 count. Tests of the suspicious white substances included with the letters revealed they were nontoxic, the complaint says.

The 2024 letters had a return address of a business office in Maryland, while the 2026 letters had a return address previously tied to a Democratic Socialists of America office. Neither of those addresses were connected to the sender, the complaint says.

The complaint says that DSA provided officials with documents showing that someone identifying themselves as “George Livingston” contacted DSA officials in October and said they would be arrested for “TREASON AGAINST THE UNITED STATES OF AMERICA.” Those messages contained some similarities to the 2024 letters, according to the complaint.

Investigators later tracked down Martin’s phone to places where the letters were sent from and also tracked his car on surveillance footage. The complaint also says investigators tracked purchases he made, including turmeric and vinegar, that could have been used to create an ink that would be visible under UV light.

The case is separate from one announced last week against an Illinois man accused of sending threatening messages to members of Congress.

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