"In what is being called an "unprecedented" situation, tens of thousands of people in Southern California were told to leave their homes Friday, with officials issuing a dire warning that a chemical tank at an aerospace facility is in "crisis" and will either fail or explode.

Firefighters initially responded to a leak at the GKN Aerospace manufacturing company in Garden Grove on Thursday, for vapor releasing from a 34,000-gallon tank containing methyl methacrylate, which is used in plastic manufacturing.

On Friday, the situation in the city, about 30 miles south of Los Angeles, had grown more dire, with officials warning that, though there was no active gas leak or plume, the tank was "actively in crisis" and unable to be secured."