The FBI is investigating suspicious letters sent to three Arizona House Democrats two weeks before the election

Three members of Congress from Arizona learned over the weekend that somebody had mailed them letters containing an unknown substance.

Representatives Adelita Grijalva, Greg Stanton and Yassamin Ansari said on Monday that state and federal law enforcement had informed them about the letters. “We will not be intimidated, and we will keep doing the work that Arizonans elected us to do,” the three wrote in a joint statement. The letters addressed to Grijalva and Ansari were sent to former office addresses. The letter addressed to Stanton's office was intercepted before delivery. The FBI's Phoenix field office and the Arizona Department of Homeland Security alerted their offices, and the FBI and the US Postal Inspection Service are investigating.

The letters did not arrive in isolation. On October 15, the Arizona Executive Tower at the state Capitol in Phoenix was evacuated after staff in the Secretary of State's office opened an envelope containing white powder. Two days before that, the Louisiana Secretary of State's office reported a similar package containing white powder. Elections officials in Ohio and Oklahoma also reported receiving suspicious packages earlier in October. No injuries have been reported in any of the incidents, as of October 20.

“Threats and intimidation will never stop us from being public servants, and we will continue doing the work that Arizonans elected us to do,” Ansari wrote on social media on Monday. The pattern, letters and powder packages aimed at members of Congress and at the officials who run elections, lands in the last two weeks of a midterm campaign in which election administration itself has become one of the contested subjects. Investigators have not said whether the incidents are connected, who sent any of them, or what the substances are.