The immediate threat of a catastrophic explosion at a damaged chemical tank in Southern California has been averted, authorities announced Monday, following an overnight inspection that confirmed a crucial crack had relieved pressure and cooled the volatile chemical inside.
Despite this positive development, evacuation orders remain in place for approximately 50,000 residents in Garden Grove, south of Los Angeles.
Officials confirmed that crews conducted temperature checks on the tank overnight, a strategy designed to minimize risks to firefighters by avoiding daytime operations when heat made conditions most dangerous.
This mission allowed crews to verify the crack and confirm falling temperatures. Orange County Fire Authority division chief Craig Covey described the results of the overnight evaluation, which showed a drop in internal temperature and pressure release, as “incredibly positive news.”
Covey stated that the decreasing temperatures and pressure release were enabling officials to “turn the corner on this incident” after days of intense concern over a potential explosion.
While there has been no chemical leak as of early Monday, the Orange County Fire Authority cautioned that the risk to public safety is “ongoing.”
Vapors began venting from the site last Thursday after the tank overheated. Firefighters have since repeatedly sprayed the tank with water in an effort to cool the chemical inside, methyl methacrylate, which is used in the production of plastic parts.
The tank’s interior temperature, which reached 100 degrees Fahrenheit (37.7 Celsius) on Sunday, had fallen to 93 degrees F (33.9 degrees C) by Monday, Covey confirmed.
Gov. Gavin Newsom declared a state of emergency on Saturday and requested President Donald Trump to issue an emergency declaration to bolster federal support for local and state officials.
The tank, located at GKN Aerospace Transparency Systems, a manufacturer of parts for commercial and military aircraft, holds between 6,000 and 7,000 gallons (22,700 to 26,500 liters) of methyl methacrylate.
Firefighters’ primary objective has been to cool the chemical to prevent a leak or explosion. Drones have been continuously monitoring temperatures at 10-minute intervals for any spikes, and containment barriers were established to prevent the chemical from entering storm drains, creeks, or the nearby ocean in the event of a spill.
Purdue University engineering professor Andrew Whelton explained that as the interior temperature rises, methyl methacrylate converts from a liquid to a gas, increasing pressure. He noted that a crack could release product or pressure, thereby reducing the chance of an explosion.
“Think of a soda can. If you leave it in a hot car it can explode,” Whelton said. “But if you put a hole in the can, the product is released and the can itself doesn’t explode.” He described an explosion that could spread the chemical over a broad area and send shrapnel flying as the worst-case scenario.
Aerial photographs showed empty streets in the evacuated areas on Sunday, with several shelters open.
At a high school in neighboring La Palma, evacuees slept in cars or on mats. Garden Grove is adjacent to Anaheim, home to Disneyland’s two theme parks, which were not under evacuation orders, though park officials were monitoring the situation.
Exposure to methyl methacrylate can lead to serious respiratory and neurological problems, as well as irritation to the skin, eyes, and throat, according to chemical fact sheets.
Whelton emphasized that if an explosion were to occur, detailed air monitoring specifically for methyl methacrylate would be crucial, rather than generic tests for volatile organic compounds, referencing the 2023 train derailment in East Palestine, Ohio. Orange County health officials noted that the chemical is easily detectable by smell, and people may notice it over a large area without being harmed.
Some Garden Grove residents filed a class-action federal lawsuit on Saturday against GKN Aerospace Transparency Systems, arguing that property values in the surrounding community are certain to be impacted regardless of the incident’s outcome.
GKN Aerospace has not commented on the lawsuit but has apologized to evacuated residents and businesses, stating Sunday it was “working around the clock to mitigate the risk of a leak.” GKN Aerospace previously agreed in 2025 to pay state regulators over $900,000 to settle violations related to recordkeeping, permitting issues, and nitrogen oxide emissions, according to the South Coast Air Quality Management District website.
