Emergency crews raced overnight to prevent a tank holding a volatile industrial chemical from exploding at an aerospace facility in Southern California.

Southern California officials have expanded an evacuation zone in several Orange County cities over a toxic chemical tank that they say is "actively in crisis."

Authorities in Orange County say they’re unable to control the valves on a tank that contains methyl methacrylate, a chemical used in the manufacture of plexiglass.

Around 40,000 people were ordered to evacuate parts of Southern California after a hazardous chemical leak at an aerospace manufacturing facility in Garden Grove triggered fears…