Authorities in Boise, Idaho, are investigating after the only Anne Frank memorial in the US was defaced with swastika stickers.

"We take all instances of hate and hate messaging seriously," the Boise Police Department said in a statement Wednesday. "We are committed to ferreting out individuals who would sow hate in our community and seek to cause harm."

Investigators are currently reviewing surveillance video, police added.

Nine stickers bearing the Nazi symbol and the words "We are everywhere" were discovered at the Anne Frank Human Rights Memorial Tuesday morning, the Wassmuth Center for Human Rights said in a Facebook post.

The center built the memorial in 2002 to honor Anne Frank's life and legacy. It features a life-size statue of the girl holding the diary in which she chronicled the 761 days she and her family spent hiding from the Nazis until they were discovered in 1944 and sent to concentration camps. Anne died in 1945 at the age of 15 at the Bergen-Belsen concentration camp.

“What makes this event actually so sad was the blatancy where [the stickers] were placed, how they were placed and the message they were proclaiming," Dan Prinzing, executive director of the Wassmuth Center for Human Rights, told the Associated Press.

The memorial was defaced in 2017 by racist and anti-Semitic graffiti that caused $20,000 in damage. The stickers found Tuesday, however, were easily removed.

Idaho has a troubled history of neo-Nazi and white supremacist sentiment dating back decades. The extremist Aryan Nations group was based in a compound in the state from the late 1970s until 2001 and in the past few years.

Last year, the Associated Press reported that white extremist groups were on the rise in the Pacific Northwest, with at least nine of them classified as hate groups by the Southern Poverty Law Center operating along the Idaho/Washington border.

In July, neo-Nazi symbols were seen among counterprotesters at a Black Lives Matter rally in Boise.

"Photos and video show several men had either tattoos or patches of the SS, a paramilitary group responsible for some of Nazi Germany’s worst atrocities," Boise State Public Radio reported.

The stickers were discovered the same day as an intense anti-mask rally in the state capital. State health officials were also forced to end a meeting on a four-county mask mandate because armed protesters outside the state capital and the homes of board members were deemed a threat to public safety.

"This is not normal — the rhetoric we've seen over the past days and months has no place in our community," Boise Mayor Lauren McLean said in a statement Wednesday. "Bad actors who use racist and violent rhetoric are not welcome in this community."

At a news conference Thursday, McLean said Boise residents need "to reckon with the fact that this act is symbolic of some of what is in our community" and work to move through it.

"We are at, if not immediately, reaching a tipping point," Rabbi Daniel Fink of Boise's Congregation Ahavath Beth Israel also told reporters.

He cited Kristallnacht, the Nov. 9, 1938, night when Nazis across Germany destroyed synagogues and vandalized Jewish businesses — a moment he described as the beginning of the Holocaust.

"Think back on that night in the events of recent dates [when you see] a swastika on the book on that statue that represents Anne Frank’s diary," he said. "This kind of mob rule where people are storming the homes of our government officials — they represent the kind of intimidation and fear and essentially the effort to strike fear through a kind of terror.

"We know where that goes. The spiral of injustice. It reminds us how things unfold if good people don’t stop it. And it’s better to stop it earlier than later."

Since Tuesday, Boise residents have left flowers and signs at the memorial condemning the vandalism.