Crowds flipped cars, pulled down light poles and removed stop signs.
It started around 11:30 Tuesday night when two large groups converged. People threw objects at officers attempting to break up the crowd, according to Commander Geoff Huff of the Ames Police Department.
"We're not sure what started it at this point," Huff said.
One person was injured when he was struck in the head with a falling light pole.
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