Oklahoma man charged over mystery powder mailings

A federal court in Oklahoma City has heard the first details of a case involving a man who sent hundreds of letters containing white powder to government offices.

The first key fact concerns the substance itself. FBI court filings released Tuesday stated that the powders tested positive for yeast or flour. Not every envelope received a full chemical analysis, but the material was not hazardous.

The second point identifies the defendant and his charges. Robin Martin was accused of conveying a hoax and mailing threatening communications. He appeared in court on Tuesday afternoon for his initial hearing. No attorney was listed in online records to speak for him at the time of the filing.

The third point addresses the timing and reach of the campaign. The letters were sent to congressional and election offices nationwide. The mailings occurred ahead of both the 2024 and 2026 elections. Federal authorities first announced the investigation last month.

Officials initially urged recipients to treat the mail as potentially hazardous. A message from the Senate Sergeant at Arms noted that law enforcement was working to intercept remaining letters. The office acknowledged that some envelopes may have already reached their intended destinations. The FBI and the Postal Inspection Service led the joint inquiry. The U.S. attorney’s office handled the formal charging process on Tuesday.