Police in the U.S. city of Oakland swept through \"occupy\" protesters\' encampment Tuesday morning, arresting 85 people mostly for unlawful assembly and illegal lodging. Several hundred officers in riot helmets began making arrests shortly before 5 a.m. local time and removed tents at the Occupy Oakland protest in a plaza outside the City Hall, and arrested at least six more at a smaller encampment at a local park around 6:15 a.m., according to San Francisco Chronicle. City officials said that they had been forced to clear the encampments because of sanitary and public safety concerns, said the report. Officers fired two or three nonlethal projectiles from a shotgun at protesters who threw bottles, cans and other objects, said local authorities. No injuries were reported. Protesters have vowed to return, but police have begun erecting metal barricades around the plaza after the clean-up action. Oakland is a major West Coast port city on San Francisco Bay in the U.S. state of California.