Portland Police officers found a crowbar, hammers, bear spray and firearms after they corralled a group of about 100 protesters, according to Fox News.
Officers surrounded the protesters because some began smashing windows.
The PD claims that they warned the crowd that failure to comply with lawful orders could result in arrest and exposure to tear gas.
Those who left were identified and photographed as part of an investigation, police said.
Others locked arms and refused; officers escorted them away and arrested them.
Protesters confronted the police, throwing rocks and full cans of beer, according to the department.
Officers used pepper spray.
Thirteen people are facing charges from the protest.
Katrina Walker, 26, of Portland, was cited for unlawful possession of a firearm; another, Tara Walker, 34, was booked for unlawful possession of a firearm and possession of a loaded firearm in a public place, among other charges.
“Both the Oregon Justice Resource Center and ACLU of Oregon are currently representing clients in federal lawsuits against PPB’s use of the kettling tactic against anti-Trump protesters in 2017. In neither case has the court approved of or found constitutional this abusive tactic.”
On Saturday, three civil rights groups called for U.S. Attorney General Merrick Garland to investigate the Portland Police Bureau in light of Friday’s arrests.
In a statement, the Oregon Justice Resource Center, the Council on American-Islamic Relations of Oregon and the American Civil Liberties Union of Oregon said: “Under the authority of Mayor and Police Commissioner Ted Wheeler and Police Chief Chuck Lovell, what PPB did last night — kettling — is an aggressive and indiscriminate police tactic of surrounding and boxing in a group of people and blocking off all exit points.
Portland has been the site of frequent protests, many involving violent clashes between officers and demonstrators, ever since the police killing of George Floyd in Minneapolis in May. Over the summer, there were demonstrations for more than 100 straight days.
Mayor Ted Wheeler has decried what he described as a segment of violent agitators who detract from the message of police accountability and should be subject to more severe punishment.