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FORT COLLINS, Colo. (AP) - The Fort Collins police chief says investigators are reviewing video from officers and the public to identify who instigated a riot-like disturbance last weekend.

Police say at least three parties were registered in the Summerhill neighborhood Saturday night, with 400 attendees expected at the largest. Registering a party with CSU and the city means police give organizers a warning if neighbors complain. Police respond to the party if there are more complaints after that.

The Coloradoan reports police went to break up the parties late Saturday after organizers received warnings, but instead of leaving, some people in the crowd threw rocks and bottles at officers. Police Chief John Hutto says officers then donned riot gear and used tear gas and pepper spray to force hundreds of people to leave.