Suspicious letters were sent to local elections officials in at least four states, the authorities said on Thursday, including to two locations in Washington State that were said to include white powders containing the toxic drug fentanyl.
Preliminary tests indicated that letters sent to at least two of four Washington election offices — in Spokane County and King County, which includes Seattle — contained fentanyl, law enforcement officials said.
Georgia authorities said that a letter bound for the election office in Fulton County, which includes much of Atlanta, had been flagged as potentially including fentanyl but had not yet been delivered. And California authorities said that they were uncertain what was in letters sent to election offices in Sacramento and Los Angeles.
Fentanyl can be fatal if ingested even in small doses, but in general, experts say, skin contact such as what might occur when opening a letter poses little risk. None of the affected election offices reported that any employees were injured.
The letters come as election offices nationwide are seeing a growing array of threats and aggressive behavior that has followed baseless charges of election fraud in recent years.
Beyond the two California cities and Georgia, the letters targeted election offices in Lane County, Ore., which includes Eugene; and King, Spokane, Pierce and Skagit Counties in Washington.
At least two of the mailings were reported to include messages, but beyond an apparent call to stop the election sent to the Pierce County Elections office in Tacoma, their nature was unclear. The Pierce County mailing included a white powder later identified as baking soda.
The F.B.I. and the U.S. Postal Service are investigating the letters, most of which arrived in Wednesday’s mail. In Washington, they arrived only days after at least two synagogues in Seattle received packages containing white crystalline or powdery substances.
Officials in the affected states called the mailings threats to the democratic process. The Georgia secretary of state, Brad Raffensperger, called on political candidates to denounce them.
“This is domestic terrorism and needs to be condemned by anyone who holds elected office and wants to hold elected office,” he said. “If they don’t condemn this, then they’re not worthy of the office they’re running for.” He said his own son died five and a half years ago of a fentanyl overdose.
While the mailings drew national attention, intimidation and threats of violence against election officials have become commonplace since former President Donald J. Trump and other Republican officeholders began raising claims of widespread fraud in the 2020 presidential election.
The Fulton County Department of Registration and Elections, singled out early by Mr. Trump and others claiming fraud, has been a frequent target, but hardly the only one. It was not clear whether the mailing to Atlanta had any connection to the racketeering trial against Mr. Trump and several of his allies playing out in Fulton County court.
Election offices across the country have tightened security, screening visitors and sometimes even installing bulletproof glass, in recent years.
Jena Griswold, the Colorado secretary of state, said on Thursday that she had received more than 60 death threats since she was named as a defendant in September in a lawsuit challenging Mr. Trump’s right to appear on the 2024 presidential ballot. Threats against officials statewide are common enough that her office has established a process for detecting them.
“We’re seeing a high threat environment toward election workers,” said Ms. Griswold, a Democrat.
In Oregon, “the very charged interactions with patrons, voting or not, the aggressive pursuits of staff — we’re starting to see that here as well,” said Devon Ashbridge, the spokeswoman for the Lane County Elections office. “This has been a frankly frightening situation.”
The tide of threatening behavior toward U.S. election workers has played a factor in the growing number of people leaving the profession and the difficulty in recruiting replacements.
“We do see trends in retirements, but this is on a much grander scale than we’ve ever seen before,” said Tammy Patrick, the chief executive officer for programs at the National Association of Election Officials.
The Justice Department has filed criminal charges involving election-related threats against at least a dozen people since it formed a task force on the issue in June 2021. Ms. Griswold and others say, however, that both the federal and state responses have fallen short of what is needed.
And they say they worry that the supercharged atmosphere surrounding the coming presidential election will only make matters worse.
Election workers are “our neighbors, our grandparents, Republicans, Democrats together,” Ms. Griswold said. “They didn’t sign up for a really hostile environment for participating in American democracy.”
Glenn Thrush and Jill Cowan contributed reporting.