Demonstrations against police brutality and systematic racism swept the nation over the summer, but unrest in Portland has frequently turned violent with extremist groups taking advantage of the protests.
Portland police announced Saturday that 27 arrests were made between Friday night and Saturday morning, when groups refused to vacate an area after officers advised them to leave.
Hundreds of protesters reportedly met in Kenton Park Friday, the site of several previous protests-turned-riots, before making their way to the Portland Police Association building.
Officers warned demonstrators to stay off the streets and off private property, saying they could be subject to "citation, arrest, the use of tear gas, crowd-control agents or impact munitions."
A local publication reported that by midnight, Portland police were on the streets trying to disperse crowds using smoke devices, shot impact munitions and stun grenades.
Police detained people by pinning them to the ground, leaving traces of blood where they had been, The Oregonian reported Saturday.
“After rocks were thrown at officers, an unlawful assembly was declared at the Portland Police Association offices in North Portland, and numerous arrests were made,” the Portland Police Department said in a statement Saturday.
Protesters' clothing suggested that they did not intend a peaceful protest, including helmets, gas masks and armored clothing, the statement said. They reportedly chanted “burn it down” as they marched in front of the Portland Police Association offices.
Officers waited 90 minutes in an attempt to deescalate the situation, prior to making arrests.
“Officers began to make targeted arrests and in some cases moved the crowd back and kept them out of the street. Several times officers pulled back and allowed members of the assembly an opportunity to leave,” the statement said.
The majority of arrests made were of Portland or Oregon residents, though one West Virginia man and a Washington state man also were arrested.
Another individual’s address was unknown at the time of the statement’s release.
The Associated Press contributed to this report.