Senior Capitol Hill staff were warned that “multiple letters containing suspicious substances” were mailed out across the country and to multiple congressional offices on Thursday.
An email notice obtained by Fox News Digital sent to chiefs of staff, administrative managers and state directors said the U.S. Postal Inspection Service, the FBI and U.S. Capitol Police were “investigating multiple letters containing suspicious substances that were mailed to various addresses nationwide, including multiple Congressional offices.”
“Law enforcement officials are working to intercept any additional letters before they are delivered, however, it is possible that some letters may reach their destinations,” the notice from the U.S. Senate Sergeant at Arms read.
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The notice was first reported by Punchbowl News.
An FBI spokesperson declined to confirm specific instances or letters, but said in a statement that, “The FBI and U.S. Postal Inspection Service are investigating a series of suspicious mailings sent to various addresses nationwide, including Secretary of State offices and their related election offices.”
“Some of the letters contained an unknown substance, and we are working closely with our law enforcement partners to respond to each incident,” the spokesperson said. “We are also working with our partners to identify the individual or individuals responsible for the letters. This FBI and the U.S. Postal Inspection Service will continue to safeguard the public and secure elections for American citizens.”
Included in the Senate Sergeant at Arms’ notice was an image of one of the envelopes that included a return address in the top-left corner for the Democratic Socialists of America’s (DSA) headquarters in New York City.
It is unclear whether the DSA had any involvement in sending the letters. Fox News Digital reached out to the DSA for comment but has not heard back.
A representative for the organization told the New York Post that the DSA “has not occupied this office address since 2013.”
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“We are also no longer headquartered at 75 Maiden Lane,” the rep said.
The notice warned that “all suspicious letters, packages, or substances should be treated as potentially hazardous.”
Suspicious letters were also sent to state elections offices around the country. The National Association of Secretaries of State and the National Association of State Election Directors said in a joint statement that, “Those who administer our elections should never fear for their safety while carrying out their essential duties.”
“Election officials take these matters seriously and work closely with law enforcement and security partners to protect their personnel and facilities,” the organizations said. “We have security measures and contingency plans in place to respond to potential threats and emergencies while maintaining essential election operations.”
It comes on the 25-year anniversary after an anthrax-laced letter was opened by a staffer in then-Senate Majority Leader Tom Daschle’s office on Oct. 15, 2001.
Since then, Congress has drastically overhauled how it accepts mail. Packages and mail no longer come directly to the Hill, and instead are processed in facilities where they are screened and irradiated before making their way to a congressional office.