OAKLAND, Calif. (AP) — Thousands are expected to take to the streets in a Northern California city to demand California's governor ban fracking.

Fracking opponents are planning a rally Saturday in Gov. Jerry Brown's hometown of Oakland.

More than 100 environmental and community groups have signed on, and protesters are being bused in from around the state.

Some began their protest Friday outside Brown's San Francisco office. Police say 12 people were arrested when they briefly blocked public access to the building.

California is the No. 3 oil producer in the nation and has added an average of 300 wells each month for the past decade, about half of them using hydraulic fracturing or fracking.

Fracking involves injecting water, sand and chemicals to break apart underground rocks so oil and gas can escape.

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