Danger of a massive chemical explosion in Southern California reduced as temperature in tank drops

The threat of a chemical tank exploding in Southern California has significantly decreased but the danger has not been eliminated, Orange County fire officials said Monday morning.

A chemical blast could still occur, officials said, but the chance of a more catastrophic vapor explosion has been eliminated.

We want to be clear that the evacuation zones are still in play. Please abide by those evacuation zones, Orange County Fire Authority Interim Chief TJ McGovern said.

About 50,000 residents received evacuation warnings inside a potential blast zone covering about 9 square miles surrounding the GKN Aerospace facility in Garden Grove.

Crews worked overnight to investigate a crack in the chemical tank, which contains 7,000 gallons of a chemical known as MMA. Authorities said crack might ease pressure and help prevent an explosion that could hurl debris into homes miles away.

While authorities say theyre monitoring the air quality, some residents have reported symptoms of exposure. And some schools have closed and switched to online learning as a precaution.

Heres where things stand Monday:

A volatile situation

The potential consequences of increased heat or pressure in the tank teetered between two dreaded scenarios: a massive chemical leak that would infiltrate the soil and air with toxic material or a catastrophic blast that could damage countless homes and businesses.

The tank contains methyl methacrylate, or MMA, which is used to make resins and plastics, according to the Environmental Protection Agency. The chemical can cause skin and eye irritation as well as respiratory problems, the EPA said.

The tank started showing signs of trouble Thursday, when heat and pressure started building up. One of the tanks at the GKN Aerospace facility had overheated and activated a relief valve and sprinklers to cool the tank, McGovern said.

But the valves on the tank were gummed up, and the temperature inside kept escalating, officials have said.

When MMA overheats, it starts a chemical reaction that is difficult to control inside a large tank, said Elias Picazo, assistant professor of chemistry at the University of Southern California.

Here we have the potential for a thermal runaway where thats the problem in itself: The reaction produces heat, but heat also initiates the reaction, and its this vicious cycle, Picazo told CNN.

Authorities are trying to keep the tank as cool as possible to keep the chemical reactions happening inside the tank stabilized, said Elaine Bernal, a chemistry lecturer at California State University, Long Beach.

A low-volume release, where the local authorities are going to be able to monitor, neutralize, and contain a threat, is most likely, EPA Administrator Lee Zeldin told CNN on Sunday.

Right now, this is an emergency response, Zeldin said. This isnt yet an environmental response, and the scale of that environmental response will be determined based off of what happens when that tank fails.

Almost 800 state and local first responders have been deployed to respond, said Gov. Gavin Newsom, including toxicologists, hazmat teams and public health sheltering experts.

Temperature gauge maxed out

Methyl methacrylates happy place is 50 degrees Farenheit, and an increase in temperature could cause a leak or explosion, Orange County Fire Authority Division Chief and Unified Incident Commander Craig Covey said.

Officials are not sure exactly what temperature might cause the tank to ignite or explode, Orange County Fire Authority Captain Steve Concialdi said. They had no clue how hot it was inside the tank Sunday because the temperature gauge has already maxed out at 100 degrees.

But by Monday morning, the temperature had stabilized and is actually falling, Covey said. It is currently 93 degrees, down from 100 degrees. That is incredibly positive news as we turn the corner on this incident.

Authorities tried to solidify the chemical inside the tank from the outside inward on Saturday a process Concialdi likened to an ice cube freezing. But he warned those efforts may not succeed.

A couple things could happen. The tank could crack and start spilling out all that 7,000 gallons of chemical, or there could be a catastrophic explosion, Concialdi said Saturday.

On Sunday evening, two firefighters approached the tank and climbed to the top.

The fire authority released a blast zone map Saturday, outlining areas which could be affected if the tank explodes. The map shows three rings around the facility representing zones of severe, moderate and light structural damage.

GKN apologized to evacuated residents and businesses in a statement Sunday and said its working with emergency services and hazardous materials teams to monitor the condition of the affected material and are working round the clock to mitigate the risk of a leak.

We are acutely aware of the uncertainty this incident is causing and sincerely apologise for the ongoing disruption to the local community, the statement said.

Busy tourist destinations like Disneyland and another theme park, Knotts Berry Farm, are nearby but are not included in the evacuation zone.

At this time, there is no impact to Disneyland Resort due to this situation and the resort remains open to guests, the parks website said Sunday. The park said its monitoring the situation and working with local authorities.

Newsom issued a state of emergency and asked President Donald Trump for an emergency declaration to support response operations. Orange County District Attorney Todd Spitzer announced an anonymous tip line and reporting form for anyone with information about the incident or what led to it.

Residents sue tank owner

A couple who live in the evacuation zone filed a proposed class-action lawsuit against GKN Aerospace on Saturday, claiming the company negligently stored and handled MMA leading to widespread disruptions for their community.

Aside from just being evacuated, everything that they know and love is inside their home, said attorney Filippo Marchino, whos leading the class-action suit.

GKN Aerospace declined to comment on the litigation Sunday.

About 100 to 120 other residents have already expressed interest in joining the class-action case, Marchino said.

The lawsuit claims the companys handling of the chemical caused dangerous conditions by creating an ongoing risk of fire, explosion, toxic chemical exposure and environmental contamination that affected tens of thousands of residents, businesses and schools.

Some residents report symptoms

Exposure to MMA can cause nausea, dizziness and significant irritation to the lungs and nasal passages, Orange County Health Officer Dr. Regina Chinsio-Kwong said.

The chemical can produce a fruit-like scent, although smelling it does not mean you have experienced enough exposure to have symptoms, she said in another update.

Officials said the chemical has not been detected in the air, but some residents said theyve experienced symptoms.

I forgot to close the window during the Thursday night, and I regret it, said Stanton resident Van Ly, who evacuated Friday. My throat and the inside of my nose feel sore, and my wife felt dizzy Friday night.

Air should be safe outside the evacuation zone, Chinsio-Kwong said, urging people to leave the affected area.

Evacuated residents flock to shelters

Some school districts in the evacuation zone announced they would move to online learning. Garden Grove Unified School District said its 13 affected schools would remain closed until further notice, and district trustee Walter Muneton said the schools would shift to virtual learning.

The Red Cross opened a seventh shelter for evacuees Sunday as others in the area reached capacity for overnight stays.

Nearby hotels were also offering discounted rates over the holiday weekend.

Dawnedra Phillips, who lives in the evacuation zone, told CNN affiliate KABC she is taking warnings from officials seriously and staying at a shelter for evacuees in Cypress.

Im waiting it out, cause here we have our community and were supporting each other the best that we can with what we have going on right now, Phillips said. I dont care how old you are, its going to harm you one way or another.

Past inspection led to violation and settlement

GKN Aerospace says its Garden Grove location is the worlds leading provider of military transparency systems and commercial aircraft transparencies. Aircraft transparency systems include canopies, windshields and windows.

A November 2020 inspection led to a violation notice and GKN Aerospace paying a nearly $1 million settlement.

The inspection by the South Coast Air Quality Management District, or AQMD a regional pollution control agency determined the site failed to keep required records of its VOC emissions, which degrade air quality when released at harmful levels, the agency said.

Inspectors also found GKN Aerospace operated new equipment without securing a permit and used existing equipment that did not match the description in the permit, the agency said. GKN also modified permitted equipment without applying for a permit change, which is required by the agency.

The company received two orders to fix the issues in December 2020 and February 2021 but failed to comply, the agency said. It led to a notice of violation in April 2021 and a civil penalty of about $900,000 paid by GKN, the agency said.

Since the violation, the South Coast Air Quality Management District said it has been working closely with GKN to help resolve these permitting issues.

In March 2025, GKN received two more notices to comply, AQMD said. The notices requested operating records and applications for registering certain equipment and a change in facility ownership.

When reached for comment, GKN reiterated its earlier statement about working to resolve the current situation at the facility that led to evacuations but did not address any previous issues.The-CNN-Wire & 2026 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.