The powder turned out to be harmless, but officials warned that more such letters might be on their way. Another official reportedly said letters sent to television comedians Jon Stewart and Stephen Colbert warned of attacks on US senators, according to Reuters.
The Associated Press reported that Sergeant-at-Arms Terrance Gainer sent a memo to Senate offices that three state and home district offices received the letters. Spokesman Kevin Smith confirmed that one of them was received at a district office of House Speaker John Boehner (R-Ohio).
Fox News obtained the email sent by Gainer, which read, "The author of these letters has indicated that additional letters containing a powdery substance will be arriving at more Senate offices and that some of these letters may contain an actual harmful material. Although all letters received thus far have proved harmless, it is essential that we treat every piece of suspicious mail as if it may, in fact, be harmful."
An official spoke anonymously to Reuters, stating that the messages sent to Colbert and Stewart warned of letters being sent to all 100 US senators, with 10 of them containing a harmful pathogen.
The letters demanded an end to lobbying, corporate personhood and corporate money and called for a new constitutional convention, said the source. They were signed “MIB.”
The Atlantic noted that the incidents recall when letters laced with Anthrax were mailed to senators and media outlets in 2001.