Authorities in Orange County, southern California, have ordered the evacuation of more than 40,000 people after a storage tank containing a highly flammable chemical at an aerospace manufacturing facility began dangerously overheating, raising fears of a catastrophic leak or explosion. The incident unfolded in Garden Grove, a city of approximately 172,000 people located about 50 kilometres south of Los Angeles, at a facility operated by GKN Aerospace, a division of a British corporation that manufactures aircraft engines and components.

The tank in question holds around 26,500 litres of methyl methacrylate (MMA), a volatile, toxic liquid used in the production of plastics and resins. Authorities first responded with a hazmat team on Thursday after detecting a rise in the tank's temperature and off-gassing, and briefly lifted an initial evacuation order later that day. However, damage to a valve created additional complications, and by Friday the situation had worsened significantly. The evacuation zone was expanded to cover residents across six cities, and officials confirmed that the tank had visibly bulged under pressure.

Orange County Fire Authority Division Chief Craig Covey delivered a stark assessment at a Friday press conference.