Occupy protestors clashed with police on Saturday as they attempted to take over the vacant Henry J. Kaiser Convention Center.
The demonstration, dubbed "Move-In Day," was part of Occupy Movement plans to set up a commune-like establishment in the vacant building, where movement command operations could be carried out.
In an open letter to Oakland Mayor Jean Quan on Wednesday, the group warned that if police attempted to interfere with the takeover, "indefinite occupation" of Oakland's airport, port and City Hall could follow.
Police prevented attempts by the group to enter the building, only to encounter movement occupation of the Oakland Museum of California, the YMCA and City-Hall, all of which resulted in arrests.
Police told The New York Times that throughout the chaos, protestors used bottles, metal pipe, rocks, spray cans, improvised explosive devices and burning flares to attack them. Police responded with smoke, tear gas and bean bag projectiles.
Collectively, Occupy Oakland events have resulted in around 400 arrests.