The risk of a catastrophic explosion at a damaged chemical tank in Southern California has been eliminated following a close overnight inspection that confirmed a crack in the tank relieved pressure and cooled the chemical, authorities said Monday.

The results of the evaluation was “incredibly positive news,” and allowed officials to turn the corner after days of concern about a possible explosion, said Orange County Fire Authority division chief Craig Covey.

However, evacuation orders remained in place for about 50,000 people in Garden Grove, California, located south of Los Angeles. There has been no chemical leak as of early Monday, but the Orange County Fire Authority said the risk to public safety is “ongoing.”

Covey didn’t say in the recorded message what the most likely outcome might be but officials had previously said they hoped to cool off the chemical inside the tank so it wouldn't leak or explode. The tank’s interior had cooled to 93 degrees F (33.9 degrees C), Covey said, down from 100 degrees (37.7 Celsius) Sunday.

After the tank overheated Thursday and began venting vapors, firefighters have repeatedly sprayed the tank with water in an attempt to cool the chemical inside, methyl methacrylate, which is used to make plastic parts. As the interior temperature rises, methyl methacrylate converts from a liquid to a gas and increases the pressure, according to Purdue University engineering professor Andrew Whelton.

GKN is a British company that supplies aircraft manufacturers

The tank is at a site owned by GKN Aerospace Transparency Systems, which makes cockpit windows, canopies and windshields for military and commercial aircraft.

The tank holds 6,000 to 7,000 gallons (22,700 to 26,500 liters) of methyl methacrylate used to make plastic parts.

GKN Aerospace, a British industrial company, says on its website that it employs about 16,000 people across 32 manufacturing sites in 12 countries and supplies technologies and components used by major commercial and military aircraft manufacturers worldwide.

It remained unknown when the operation would reopen.

Disruptions at facilities producing specialized aircraft components can be difficult for the global aerospace industry to absorb because supply chains are highly concentrated globally and already strained, said Richard Aboulafia, managing director of the aerospace consulting firm AeroDynamic Advisory.

Aboulafia said aerospace manufacturing differs from many other industries because aircraft production rates are relatively low, leaving only a small number of suppliers for many specialized parts and systems.

“There’s just not a lot of margin in the system,” he said.

Dealing with displacement and health concerns

Aerial photos taken by The Associated Press showed streets in the area were empty Sunday, while several evacuation shelters were open.

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 situation.

Exposure to methyl methacrylate can cause serious respiratory problems, neurological problems and irritation to the skin, eyes and throat, according to fact sheets about the chemical.

Orange County health officials said the chemical is easy to smell and people may notice it over a large area without being harmed.

Residents taking legal action

Some Garden Grove residents filed a class-action federal lawsuit Saturday against GKN Aerospace Transparency Systems. Lawyers for the residents argued that regardless of what happens, property values in the surrounding community are sure to be impacted.

GKN Aerospace did not comment on the lawsuit but has apologized to residents and businesses forced to evacuate. It said Sunday it was “working around the clock to mitigate the risk of a leak.”

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

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Associated Press journalist Ethan Swope in Garden Grove, California, contributed to this report.