The handwritten and threatening letters had Omaha, Neb., postmarks and no return addresses, and were each mailed July 25, an internal alert from Senate Sergeant at Arms Terrence Gainer said.
They were caught at a Senate mail-screening facility and never arrived at the legislators' offices. Although they are being tested for hazardous materials, the substance inside the envelopes appeared to be sugar, the Washington newspaper Politico reported.
Among those to whom the letters were addressed are Michael Bennett, D-Colo., Carl Levin, D-Mich., Chris Coons, D-Del., Mark Begich, D-Alaska, Dianne Feinstein, D-Calif., Claire McCaskill, D-Mo., John McCain, R-Ariz., Bob Corker, R-Tenn., Saxby Chambliss, R-Ga., and Tom Coburn, R-Okla.
Notable deaths of 2014 [PHOTOS]
Hiker dead in apparent bear attack in New Jersey