Washington - Simmering grievances, political divides, a steady proliferation of online neo-Nazi propaganda, and the approach of the 2024 presidential election are keeping the United States stuck in a "heightened threat environment," according to the latest warning from U.S. homeland security officials.

The Department of Homeland Security reissued a National Terrorism Advisory System bulletin Wednesday, saying a combination of anger, ideologies and opportunities "pose a persistent and lethal threat to the Homeland."

This is the eighth time DHS has issued the bulletin since 2021, with this advisory replacing the previous warning, issued last November.

It comes just days after a 19-year-old man from the state of Missouri crashed a rented truck into a White House security barrier before waving a Nazi flag, and as the nation marks the first anniversary of a school shooting in Uvalde, Texas, that left 19 children and two teachers dead.

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"Recent tragic events highlight the continued heightened threat environment our nation faces," Homeland Security Secretary Alejandro Mayorkas said in a statement.

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"These threats are driven by violent extremists who seek to further their ideological beliefs and personal grievances," he said. "We are working with partners across every level of government, within the private sector, and in local communities to keep Americans safe."

As with previous advisories, the latest bulletin warns the biggest threat comes from individuals and small groups prepared to act either on personal grievances or a range of ideological beliefs.

"We continue to hear and see calls from domestic violent extremists based on ideological views, calls for violence," according to one senior official, who briefed reporters on the condition of anonymity under ground rules set by DHS. "The tempo and the seriousness of those kinds of calls is still high and happening on a regular basis."

For example, the DHS bulletin points to the May 6 shooting in Allen, Texas, noting the gunman, Mauricio Garcia, espoused both white supremacist and involuntary celibate, or "incel," beliefs.

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It also highlighted a series of criminal acts in Georgia dating back to 2022, with the suspects allegedly citing a range of views - from anarchism to animal rights - for plotting an attack on a planned public safety training center.

And government facilities are just part of a long list of potential targets, which includes the country's critical infrastructure, faith-based groups, those associated with LGBTQIA+ community, racial and ethnic minorities, and schools.

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Senior homeland security officials said Wednesday that part of what makes the threat environment so dangerous is that the targets, like in some recent school shootings, may have little or nothing to do with an attacker's motivation.

"It's not even clear that the school itself was actually tied in any way to the person's ideological narrative or grievance," said a second senior homeland security official, who like the first briefed on the condition of anonymity. "It just serves as an opportunistic target."

The official said that despite the serious concerns, there is no intelligence at this time to suggest specific groups or individuals are preparing for attacks. But some of the trends are worrisome.

"There does seem to be an increase in the calls for violence based on the neo-Nazi, white nationalist kind of theme," said the first official.

"That [neo-Nazi] theme is being propounded more effectively now than it was several years ago," the official added, saying that several prominent white supremacists' texts have been gaining traction in online forums after being converted into audiobooks.

Homeland security officials said they are also tracking the impact of calls, both publicly and online, for violence against migrants coming to the U.S. southern border.

And they see a potential for danger as candidates start announcing their intentions to run for president and the 2024 election cycle gets underway.

"We expect that questions or concerns that individuals may have about that election cycle and the election process could, in fact, become a source of motivation for an individual to go that extra step toward a violent extremist act," the second official said.

The danger will grow, he said, "if the terminology surrounding the election starts to talk about it in existential or apocalyptic terms."

Additionally, DHS officials said they continue to worry about threats from nation-state actors like Iran, as well as the potential threat from terror groups like Islamic State and al-Qaida, though some officials in recent months have downplayed the likelihood of a foreign terror attack on U.S. soil.

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