Washington — Threat actors are likely to leverage claims of election fraud to drive election-related violence, according to a federal bulletin obtained by CBS News.

"Some individuals are calling for violence as a response to election fraud narratives, primarily targeting election officials and populations that threat actors perceive as threatening the integrity of the 2024 general election," the bulletin says.

The bulletin, which was published Monday by the Department of Homeland Security, warned that online forums used by domestic violent extremists contain threats of violence against election officials and infrastructure "to prevent perceived fraud or to retaliate against it." Many of the posts are promoting narratives about election fraud linked to mail-in ballots or electronic voting machines, it said.

"Some individuals motivated by this narrative have stated their intent online to intimidate voters or elections staff through surveillance of election infrastructure or personnel, including by armed individuals," the bulletin continued. "Some of these online users have encouraged violence against ideological opponents related to the use of mail-in voting while others promoted methods of sabotaging ballot drop boxes. Other individuals are using online forums to call for violence against local election officials in response to allegations of fraud."

Federal investigators believe there are several factors that could increase threat actors' perceptions of election fraud, including "a contested or close election, variations in state election laws and regulations impacting the release of results, unforeseen events that delay vote counting, or technological or administrative errors impacting vote counting processes."

The warning comes as ballot boxes have been set on fire in Portland, Oregon, and Vancouver, Washington, destroying hundreds of ballots. A number of mail-in ballots were also damaged when a U.S. Postal Service mailbox was recently set on fire in Phoenix, Arizona. The incidents are under investigation.

Last week, intelligence and law enforcement agencies said Russian actors had "manufactured and amplified" a video purporting to show someone destroying mail-in ballots in Bucks County, Pennsylvania "as part of Moscow's broader effort to raise unfounded questions about the integrity of the U.S. election and stoke divisions among Americans."

A joint intelligence bulletin issued earlier this month by the Department of Homeland Security and FBI warned of the potential for domestic violent extremists "with election-related grievances" to target political candidates and elected officials in the coming weeks. It said domestic extremists "pose a threat of violence to a range of targets directly and indirectly associated with elections through at least the presidential inauguration" on Jan. 20, 2025.

A Department of Homeland Security spokesperson said Monday that the U.S. remains in a "heightened" threat environment.

"The Department continues to advise federal, state, and local partners to remain vigilant to potential threats and encourages the public to report any suspicious activity to local authorities," the spokesperson said.