PORTLAND, Ore. (NewsNation) — Portland police arrested 23 people and declared a “riot” downtown after a group vandalized City Hall and smashed the building’s windows Tuesday night.

Demonstrators in the crowd of about 150 also threw bottles and eggs at police, put metal bars in the street to try to damage police vehicles and smashed a security camera on the City Hall building, police said in a statement. The statement said officers used “crowd control munitions” in response but did not say what kind.

Portland police said a group marched from Shemanski Park to City Hall at around 9:30 p.m. PT, and within minutes crowd members began spray painting and vandalizing the city building. Others entered City Hall, broke windows and smashed security features, the department said.

Police declared unlawful assembly, and eventually issued a riot declaration in attempts to get crowds to leave the area, NewsNation affiliate KOIN reported.

Officers observed a man “igniting an aerosol can while spraying it towards City Hall in an attempt to set the building on fire,” the police department said.

Police said security guards were working inside the building at the time of the fire.

“Due to the extreme life safety concerns of those working inside the building, the incident commander determined that it was a riot,” the department said in a statement.

Police said they arrested 23 adults and detained two juveniles.

Most of the charges were interfering with a peace officer or disorderly conduct, but these are charges that Multnomah County District Attorney Mike Schmidt has said his office won’t prosecute, KOIN reported.

Police said no tear gas was used in the effort to disperse crowds.

The violence came a day after protesters Monday night repeatedly set fire to a police union headquarters building and were repelled by officers spraying tear gas, officials said.

Portland has been gripped by nightly protests for nearly three months since the police killing of George Floyd in Minneapolis. Demonstrations have targeted police buildings and federal buildings. Some protesters have called for reductions in police budgets while the city’s mayor and some in the Black community have decried the violence, saying it is counterproductive.

The FBI plans to hold a media briefing Wednesday to discuss unrest in Portland, KOIN reported.

On Tuesday, President Donald Trump renewed calls to have Gov. Kate Brown and Portland Mayor Ted Wheeler call in the state’s National Guard.

“They must stop calling these anarchists and agitators ‘peaceful protestors’. Come back into the real world! The Federal Government is ready to end this problem immediately upon your request,” Trump wrote on Twitter.

Brown responded on Twitter to Trump’s demand, calling it “political theater.”

In July the federal government sent agents to protect federal property in downtown Portland. Crowds grew into the thousands and agents repeatedly clashed with people over a two-week period, deployed tear gas and arrested people they said were hurling objects and trying to hurt agents and damage property.

The agents pulled back from a visible presence downtown, but it’s unclear how many remained in Portland, under an agreement in which the Oregon State Police would be deployed to downtown. The State Police left after the agreed upon two-week monitoring period.

NewsNation is working on contacting protesters involved in the Tuesday night demonstration. Check back for more updates.

The Associated Press and NewsNation affiliate KOIN contributed to this report.