(Bloomberg) -- A fast-moving California wildfire that erupted Monday in the hills east of Sacramento forced July 4 revelers to shelter in a PG&E Corp. hydroelectric station until law enforcement escorted them out. 

About 100 vacationers and PG&E employees were evacuated from the Electra Powerhouse at about 9:30 p.m., according to the California Department of Forestry and Fire Protection, or Cal Fire. The Electra Fire, first spotted at 3:44 p.m. Monday, expanded to 3,034 acres by Tuesday morning with 0% containment, as flames raced through vegetation parched by a third year of drought.

The cause of the fire, which started as people flocked to nearby lakes and rivers for the holiday, remained under investigation.

A PG&E spokeswoman said Tuesday she was uncertain whether the powerhouse, which sits on the north fork of the Mokelumne River, sustained any damage. About 12,000 homes and businesses in the area were without power Tuesday morning, according to the utility’s website. 

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