Southern California chemical tank has a crack that could possibly lower risk of explosion

Water is sprayed on a tank that overheated at an aerospace plant in Garden Grove, Calif., Friday, May 22, 2026. (AP Photo/Ethan Swope)

A damaged chemical tank in Southern California has a crack — potentially lowering the risk of a cataclysmic explosion — though an evacuation order remains in effect for some 50,000 area residents with no timeline on when they can return, fire officials said Sunday.

Orange County Fire Authority Capt. Wayhowe Huang said that fire officials were able to evaluate the tank more closely overnight and discovered the tank had cracked.

Huang told The Associated Press earlier Sunday that it did not appear that any of the highly volatile chemicals in the tank have leaked. “There’s still the danger of a possible explosion,” Huang said.

Firefighters have been spraying the tank with water in an effort to cool the chemicals inside and prevent an explosion. The inside of the tank reached 100 degrees (37.7 Celsius) Sunday, Democratic state Sen. Tom Umberg said, an increase of 10 degrees Fahrenheit (5.5 Celsius) since Saturday.

Democratic Gov. Gavin Newsom, who declared a state of emergency Saturday, said in a post on X he had asked U.S. President Donald Trump to issue an emergency declaration to bolster federal support for local and state officials.

The pressurized tank overheated Thursday and began venting vapors at a company site in Garden Grove, about 40 miles (60 kilometres) south of downtown Los Angeles, according to the Fire Authority.

No injuries have been reported. Air monitoring tests have found that air pollution around the evacuation zone is within normal limits, and specialized equipment has been deployed to ensure no gas is released from the compromised tank, state and federal environmental officials said Saturday.

The streets were empty in the area Sunday, according to aerial photos taken by the AP.

Tank crack could mitigate damage

A crack could be a welcome development, as it could mean product or pressure inside the tank is being released, reducing the chance the tank explodes, said Andrew Whelton, an engineering professor at Purdue University.

“Think of a soda can. If you leave it in a hot car it can explode,” he said. “But if you put a hole in the can, the product is released and the can itself doesn’t explode.”

Elias Picazo, a chemistry professor at the University of Southern California, agreed that a crack could be a positive development.

“A strategic leak buys more time for the liquid within the tank to solidify as the reaction continues,” he said. “Depending on where the leak is, it can also be used to direct the unreacted liquid out of the tank in a controlled manner.”

Faisal Khan, head of the chemical engineering department at Texas A&M University, said a crack suggests an explosion could still happen -- just not in the magnitude initially feared.

“Cooling is happening on the surface of the tank while runaway reaction may be occurring deep inside the tank,” he explained. “Yes, reaction is slowed compared to what it started. However, we are not out of explosive release risk.”

Several shelters for evacuees remained open. The parking lot was full Sunday at an evacuation center at a high school in neighboring La Palma. Some people, including a family of seven, slept in cars or on mats and sleeping bags on the asphalt. The large family also had nine cats with them. They stacked up cat carriers for a makeshift table as they waited around, sipping coffee and tending to the pets.

Meanwhile, some Garden Grove residents filed a class-action lawsuit on Saturday against GKN Aerospace Transparency Systems, the company that operates the facility where the tank is located.

Lawyers for residents living in the evacuation zone argued in their federal court lawsuit that regardless of what happens next, property values in the surrounding community are sure to be impacted.

Spokespersons for the company didn’t comment on the lawsuit itself, but pointed to a Saturday statement in which they apologized to residents and businesses that have been forced to evacuate.

On Sunday, the company released another statement saying it was monitoring the “condition of the affected material” and “working around the clock to mitigate the risk of a leak.”

Officials said the valves on the tank are broken or “gummed up,” which prevented crews from removing the chemical or relieving the pressure on the tank, said Craig Covey, Orange County Fire Authority division chief.

Firefighters’ first hope is to find a way to cool off the chemical inside the tank so it won’t leak or explode. If that is not possible, Whelton said it would be best if the tank sprang a leak so the chemical could be mostly contained. An explosion that could spread the chemical over a broad area and send shrapnel flying would be the worst-case scenario.

If the temperature inside the tank continues to increase, the pressure will continue to build as the methyl methacrylate converts from a liquid to a gas. Whelton said it’s unlikely that firefighters would consider creating a hole in the tank because of fears that could create a spark that might ignite the volatile and flammable gas.

Drones were monitoring temperatures at 10-minute intervals to watch for any spikes, Covey said on a social media post on X. Containment barriers have been set up to prevent the chemical from getting into storm drains or reaching creeks or the nearby ocean in the event of a spill, Covey said.

Exposure could lead to health problems

The damaged tank is located at GKN Aerospace, which makes parts for commercial and military aircraft. It holds 6,000 to 7,000 gallons (22,700 and 26,500 litres) of methyl methacrylate, used to make plastic parts.

GKN agreed to pay state regulators more than US$900,000 in 2025 to settle violations involving recordkeeping, permitting issues and nitrogen oxide emissions, according to a report on the South Coast Air Quality Management District website.

Exposure to methyl methacrylate can cause serious respiratory problems and even render someone unconscious. It can also cause neurological problems and irritate the skin, eyes and throat, according to fact sheets about the chemical. But Orange County health officials said the chemical is easy to smell and residents may notice it over a large area without being harmed.

Whelton said the volume of chemical in the tank is much smaller than in the disastrous 2023 train derailment in East Palestine, Ohio, which he studied when more than 115,000 gallons (435,000 litres) of vinyl chloride was released after officials blew open five tank cars and burned the chemical.

“Many of these are acute, fast-acting effects. But the longer somebody stays in contact with it, the more potential for significant damage that occurs,” Whelton said.

If an explosion releases the chemical into the air, Whelton said, it will be crucial to conduct detailed air monitoring specifically for methyl methacrylate and not just generic tests for volatile organic compounds as officials did in East Palestine.

The weather will be an important factor in determining where a plume of chemicals would go in the event of an explosion. Officials were developing maps to predict different scenarios.

Garden Grove is next to Anaheim, home to Disneyland’s two theme parks, which were not under evacuation orders. Park officials said they were monitoring the incident and supporting employees impacted by evacuations.

By Philip Marcelo

Marcelo reported from New York. Associated Press journalist Ethan Swope contributed to this report.