Brown said Wednesday that he acted based on the requests of local residents and the "prolonged and continuing" nature of the gas blowout at the underground storage facility.
The leak was first discovered Oct. 23 by crews at the Aliso Canyon storage facility near Northridge. Southern California Gas Co. officials initially said the issue would be resolved in a few days or weeks but later said the leak could actually take months to fix.
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County health officials say they have received reports of residents experiencing nosebleeds, dizziness, nausea and headaches linked to the leak and have ordered Southern California Gas Co. to offer free, temporary relocation to area residents.
The leak is gushing 1,200 tons of methane daily, along with other gases. No evacuation order for the area has been issued but 700 families have voluntarily left the area and another 1,000 are applying for relocation services, officials said.
Southern California Gas Co., which has been working to fix the leak, insists there are no health risks to residents.
Los Angeles County and the Los Angeles school board already have declared the crisis an emergency, moving students out of two schools in the neighborhood.
The governor's move, among other measures, directs efforts by California agencies in stopping the leak, and it orders emergency regulations for other gas-storage facilities throughout the state.
The Associated Press contributed to this report.