More than three dozen members of Congress have seen their offices targeted with envelopes containing white powder in recent days, prompting evacuations and investigations by federal authorities.

Law enforcement sources reported that over 100 such letters are circulating in the U.S. mail system. Preliminary tests indicated the substance is not hazardous, though additional lab analysis continues. The FBI, U.S. Capitol Police, and U.S. Postal Inspection Service are leading the probe into the mailings, which began surfacing earlier this month.

The latest incident occurred Monday when an envelope arrived at the Leesburg district office of Virginia Democrat Suhas Subramanyam, leading to a quick evacuation. Subramanyam's office stated that initial tests confirmed the powder posed no hazard. He described the act as political intimidation with no place in the country.

Both parties have been affected. Democratic targets included Senate Minority Leader Chuck Schumer, whose letter was intercepted, along with Sens. Alex Padilla of California, Chris Murphy of Connecticut, and Kirsten Gillibrand of New York. In the House, offices of Reps. Hakeem Jeffries, Ritchie Torres, and Tom Suozzi in New York saw staff exposure to the powder. Republican senators Mike Rounds of South Dakota, Pete Ricketts of Nebraska, and Ted Cruz of Texas also reported suspicious letters at their offices.

State election offices in at least 15 states, including Louisiana, Oklahoma, Ohio, and others, received or had letters intended for them. Many were intercepted before delivery. The timing, less than three weeks before the November 3 midterms, has heightened concerns among officials.

Authorities noted common features in some envelopes, including processing through certain mail centers and return addresses linked to a New York City location associated with the Democratic Socialists of America in one reported image. No suspects have been identified, and no injuries resulted from the incidents. Offices resumed normal operations after clearances.

The mailings echo past threats to public officials but have so far proven inert based on available testing. Investigators continue efforts to trace the source and intercept remaining letters.