PORTLAND, Ore. - More than 400 people spilled out onto a residential street in the college town of Eugene, throwing bottles at officers, breaking car windows and tearing down street signs, police said Saturday.
A YouTube video shows the scene as police used tear gas.
No injuries were reported during the riot late Friday in the West University neighborhood. Police arrested nine people, mostly on alcohol-related charges.
Eugene police spokesman Doug Mozan said it's unclear what touched off the rioting. The town is the home of the University of Oregon, which has about 17,000 undergraduates.
"It's a high-density residential area chockfull of student renters in some very large houses with basements (that) can hold a couple hundred people each," Mozan said. "If people start to spill into the street and get drunk enough, sometimes they engage in group-think. It was like a flash mob, almost."
Eugene police said in order to break up the crowd, they needed 50 officers that included members of the Oregon State Police, Lane County sheriff's office and Springfield police department.
Among the nine arrests were Odin Erickson, 24, who was charged with rioting, interfering with police and two counts of third-degree criminal mischief. Derek Brown, 19, was charged with second-degree disorderly conduct and being a minor in possession of alcohol.
"It is disappointing that at this early point in the year, the West University neighborhood is subjected to this type of drunken, violent behavior," said Eugene police chief Pete Kerns. "The police department will do everything we can with neighbors, businesses and the university to reduce the likelihood that this will happen again."
The University of Oregon said it would issue a comment later Saturday.
Eugene police are no strangers to rowdy student parties spilling into residential streets or riots. On Sept. 25, 2008, police confronted about 250 people in the same neighborhood, and one police car was struck with a bottle.
One of the worst incidents in the neighborhood unfolded on Halloween in 1998, when 12 people were arrested after rioters caused damage and injuries.