Police in the northwestern U.S. city of Portland, Oregon, used tear gas Wednesday night to disperse protesters at a building that houses a police precinct and jail.Authorities declared the latest in what have been several months of nightly protests a riot and said some demonstrators engaged in criminal activity that included setting fires and lighting fireworks outside a federal courthouse.The protests began after the death in police custody of George Floyd in the state of Minnesota, with those in Portland and many other places across the country calling for police reforms and steps to address racial inequality.Portland gained prominence when federal agents deployed there in July over the objections of local officials.They have since withdrawn.