Tens of thousands of Southern California residents were told to leave their homes after officials warned that a leaking chemical tank in Orange County could spill toxic material or explode.

According to The Guardian, authorities in Orange County ordered about 40,000 people to evacuate after a storage tank at a GKN Aerospace site in Garden Grove began releasing gas and appeared close to failure.

"We have a tank that is actively in crisis," Orange County Fire Authority Division Chief Craig Covey told reporters at a news conference.

The tank contains methyl methacrylate, a highly flammable substance used in the production of resin and plastics.

Emergency crews first responded on May 21, and evacuation orders were initially issued and later lifted.

Officials said the situation worsened after valve damage caused additional operational problems and prevented crews from fully resolving the issue, prompting a broader evacuation order on Friday.

The evacuation zone expanded to include residents in Garden Grove, Cypress, Stanton, Anaheim, Buena Park, and Westminster.

Officials said the two most serious scenarios are the release of about 6,000 to 7,000 gallons of the chemical or a heat-driven chain reaction that could lead to a blast involving nearby tanks.

"This thing is going to fail, and we don't know when," Covey said, per The Guardian. "We're doing our best to figure out when or how we can prevent it."

Methyl methacrylate can harm people and the surrounding environment.

County health officer Dr. Regina Chinsio-Kwong said heating the chemical can give off fumes linked to breathing trouble, burning or itchy eyes, nausea, and headaches.

If the tank spills, officials are trying to keep the hazardous material from flowing into drainage systems, nearby creeks, or the ocean.

Garden Grove lies roughly 30 miles southeast of downtown Los Angeles and near Disneyland, though the theme parks were not under evacuation orders Friday.

Hazmat crews and local officials have been working to contain the risk while preparing for the possibility that the tank could rupture.

Crews have placed sandbag barriers to limit the spread of any spill into drains and other waterways.

Authorities also expanded evacuation orders as conditions changed rather than waiting for the situation to deteriorate further.

A sudden tank failure or blast could strike neighboring industrial tanks containing fuel or other chemicals.

Police and emergency officials have also been urging residents to comply.

Garden Grove police chief Amir El-Farra said a noticeable portion of those ordered to leave were still not doing so.

"We are setting up these evacuations in preparation for these two options: it fails or it blows up," Covey said. "Please follow our requests and orders for evacuations."

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