Mass Evacuation Ordered in California as Chemical Tank Leak Sparks Explosion Fears

Tens of thousands of residents in California were ordered to evacuate after a leaking chemical storage tank sent toxic fumes into the air and raised fears of a potentially devastating explosion in a densely populated part of Orange County.

Emergency crews spent Friday battling to stabilise the damaged tank in the Garden Grove area, southeast of Los Angeles, where officials warned the situation remained dangerous despite progress in cooling the container.

The tank contained about 7,000 gallons of methyl methacrylate, a highly flammable chemical widely used in the production of plastics. Fire officials said the leak created two serious possibilities: a large-scale spill or a thermal runaway reaction that could trigger an explosion.

Incident Commander Craig Covey described the threat in stark terms during a press briefing.

“There are literally two options left,” Covey said. “The tank fails and spills a total of about 6,000 to 7,000 gallons of very bad chemicals into the parking lot, or the tank goes into a thermal runaway and blows up, affecting nearby tanks that contain fuel and chemicals.”

Authorities said evacuation orders were issued to prepare for either outcome.

Garden Grove Police Chief Amir El-Farra said approximately 40,000 people were impacted by the evacuation zone, although several thousand residents chose to remain despite repeated warnings from officials.

Television aerial footage showed firefighters spraying large streams of water onto the tank, which has a total capacity of 34,000 gallons, in an effort to lower its temperature and prevent a dangerous reaction.

By Friday evening, officials reported signs of improvement.

Covey said cooling efforts had successfully reduced the tank’s temperature to around 61 degrees, closer to the safer operating level of 50 degrees.

“Our group is going to do everything they can to come up with a third, a fourth, a fifth option,” he said in a video update.

Health officials defended the broad evacuation perimeter, stressing that the exclusion zone was necessary to protect the public should conditions worsen.

Orange County health officer Regina Chinsio Kwong urged residents to remain alert and report any unusual odours.

“If it does explode and there is a vapor, you are all safe as long as you are out of the evacuation zone,” Kwong said.

She asked people to notify authorities if they detected what she described as “a fruity and heavy smell,” associated with the chemical.

Officials said no injuries had been reported as of Friday evening, and investigators had not yet determined the cause of the leak, which was first reported Thursday.

Emergency teams were also preparing containment barriers to stop any chemical spill from entering storm drains and waterways that flow toward the Pacific Ocean.

According to the US Environmental Protection Agency, methyl methacrylate can irritate the skin, eyes and respiratory system, with both short- and long-term exposure linked to breathing difficulties and neurological symptoms.

Covey said crews were preparing for what he called the “best-case scenario” of a controlled spill, which would be far less dangerous than an explosion and widespread toxic plume.