Riot police from a number of Bay Area departments fired tear gas and other projectiles early Thursday and arrested dozens of demonstrators to break up Occupy Oakland protests that had drawn thousands of participants Wednesday.

Officers moved in near the City Hall encampment where tents re-sprouted after officials last week ordered them razed. The police action came after a predominantly peaceful day of protest that attracted more than 7,000 people of all ages and left-leaning political stripes.

The evening appeared to be winding down peacefully when protesters declared victory at the Port of Oakland at 9 p.m.  Wednesday -- after authorities confirmed that a shift scheduled to start work at 7 p.m. had been canceled. But as demonstrators amassed again at the City Hall plaza, the situation devolved.