With pressure building inside a tank of hazardous chemicals in Southern California, firefighters racing to stop an explosion or toxic leak have turned to outside specialists in a bid to avert disaster, as several nearby shelters filled up with evacuees. Evacuation orders stayed in force across a zone affecting tens of thousands of residents in Garden Grove, a Los Angeles-area suburb. California Governor Gavin Newsom declared a state of emergency in Orange County, while his office urged residents to comply with evacuation…