Despite a day of peaceful protests, which led to the closure of the Port of Oakland, some participants of Occupy Oakland turned violent Wednesday night. The clashes between protesters and police came after demonstrators gathering at City Hall plaza gained entry into a nearby empty building. A small group of protesters set trash on fire to make a barricade to discourage police. Early in the morning police used tear-gas and flashbang grenades to clear the crowd from downtown streets. As many as 40 protesters were arrested.