WASHINGTON – The powder in a letter sent to Rep. Adelita Grijalva tested negative for anything harmful, an aide to the Tucson Democrat said Tuesday.

But that and other suspicious letters sent in recent days to other Arizona lawmakers and the state’s top elections official are raising concerns about political intimidation on the eve of the midterm elections.

“One envelope can frighten an entire institution, and the powder doesn’t need to be lethal for the intimidation to work,” said Murat Haner, a criminology expert at Arizona State University who studies terrorism and political violence.

Brooke Brennan, a spokeswoman for the FBI’s Phoenix Field Office, told Cronkite News the FBI and U.S. Postal Inspection Service are investigating a series of suspicious mailings across the country.

“Some of the letters contained an unknown substance, and we are working closely with our law enforcement partners to respond to each incident” and to find whoever sent the letters, she said in a statement.

More than three dozen congressional and election offices in 32 states have been sent suspicious mail in recent days, Axios reported Tuesday. Recipients included lawmakers in both parties.

On Monday, the House Sergeant at Arms told lawmakers that tests on letters sent to congressional offices have not shown any dangerous substances, according to Roll Call.

In Arizona three federal lawmakers, all Democrats, said Monday that their offices had been targeted: Grijalva and Phoenix Reps. Greg Stanton and Yassamin Ansari.

“We will not be intimidated, and we’ll keep doing the work that Arizonans elected us to do,” they said in a joint statement.

Laurel Harbridge-Yong, a Northwestern University political scientist whose current research focuses on political violence and how threats against elected officials shape legislative behavior, said white powder is frightening and sure to draw attention.

But such incidents are only part of a “much more widespread problem,” she said, adding, “The psychological toll on office holders and their family is significant.”

She said these incidents can dissuade some politicians from pursuing controversial policies or seeking office, but many are resilient and determined to continue their work.

On Oct. 15, staff at the Arizona Secretary of State’s office opened a letter filled with a white powder, causing an evacuation of the State Capitol Executive Tower.

Secretary of State Adrian Fontes said afterwards that his office will be on “high alert” but “we will not be scared out of doing our jobs on behalf of the voters of Arizona.”

Last week, the House and Senate Sergeant at Arms offices, which oversee safety and security for members of Congress, warned lawmakers and their staff to be careful in handling incoming mail after a string of suspicious incidents.

The letters to Grijalva and Ansari were sent to former office locations, according to their joint statement.

Ansari told KTAR News on Monday that the letters to all three Arizona lawmakers contained a white powder.

“The best response is to take every incident seriously, not amplify panic, and make sure election workers and local officials have support and security. Most of them are not high-profile people,” Haner said by email.

Nate Sigal, a spokesperson for Grijalva, said the office receives threats “fairly frequently,” though not usually by mail, and refers those to the U.S. Capitol Police.

The Capitol Police reported in January that its Threat Assessment Section investigated 14,938 concerning statements, behaviors and communications directed at members of Congress, their families, staff and the Capitol in 2025, up by more than 5,000 over the previous year. 

Haner said incidents of political threats began to escalate in 2016, and intensified in 2020 when election administrators became targets.

“Threats are now more frequent, more personal, and increasingly aimed at the people and institutions that make democracy function: election workers, local officials, members of Congress,” he said.

This article first appeared on Cronkite News and is republished here under a Creative Commons Attribution-NoDerivatives 4.0 International License.