New Delhi, May 23 -- Authorities warn a leaking methyl methacrylate tank at a Garden Grove aerospace facility could either rupture catastrophically or trigger a toxic plume, leaving tens of thousands with no option but to flee.

Emergency authorities issued sweeping evacuation orders for roughly 40,000 residents across multiple cities in Orange County, California, on Friday after a large chemical storage tank at an aerospace manufacturing facility began leaking a volatile and flammable substance, raising the spectre of a catastrophic explosion or a mass toxic release.

The incident is centred on a tank at a GKN Aerospace facility on the 12100 block of Western Avenue in Garden Grove, approximately 35 miles south-east of downtown Los Angele...