PORTLAND, Ore. (AP) — Protesters returned to the streets of Portland, following a pause largely due to poor air quality from wildfires on the West Coast.

Police declared an unlawful assembly Friday night in a neighborhood near a U.S. Immigration and Customs Enforcement building where protesters had marched. Demonstrators participated in criminal activity and threw items at officers, police said, leading to 11 arrests.

Demonstrators had not gathered in the city since at least September 9, when police and protesters clashed near City Hall. Wildfires have spewed dangerously dirty air across Oregon, California and Washington state, and sent haze across the country.