Authorities said dozens of protesters marched towards the Portland Police Association (PPA) office on Monday, before vandalizing the building and setting fire to a nearby billboard.
Authorities said that when the group arrived, a sound truck gave three announcements requesting that protesters stop blocking traffic, “be courteous to your neighbors,” and not vandalize buildings.
“The group immediately began spray painting the PPA office,” the police said, adding that some protesters climbed onto roofs of nearby businesses and used signs to block traffic and occupied a roadway.
At one point, an unidentified individual set fire to a nearby billboard.
“The fire burned the attached advertisement as the rest of the structure appeared to remain unaffected by the fire. The fire appeared to extinguish itself,” the police said.
Portland police issued another warning, calling on the crowd to stay on the sidewalk, stay off buildings, and “not light fires.” They threatened to arrest people engaging in criminal activity and warned that they may deploy crowd control measures, including batons and tear gas.
The crowd dispersed around midnight, with police saying no arrests were made.
The PPA building was earlier the target of protests, with police in August declaring a riot after the office was defaced with graffiti and a fire was set nearby.