Crack suspected in chemical tank as evacuations continue

Southern California emergency officials say an overnight reconnaissance mission at the GKN Aerospace facility in Garden Grove found a potential crack in a volatile methyl methacrylate storage tank, a development that could shift how responders cool and manage

By early Sunday, the answer responders had been chasing for days had finally appeared—if only through a late-night glimpse.

Southern California emergency officials announced that a firefighter reconnaissance mission overnight found a potential crack in a volatile chemical tank at the GKN Aerospace facility in Garden Grove. Fire Chief TJ McGovern said the discovery could change the response to the days-long hazardous materials incident. which has kept tens of thousands of residents out of their homes.

In a video update shared on X. McGovern said the team identified “a potential crack in the tank. ” adding that the crack could “potentially be relieving some of the pressure in there.” If that proves true. it would mean responders might be able to adjust their approach and begin planning for lifting evacuation orders.

For days, authorities have been working to keep the overheated tank from exploding. Officials described the chemical situation as highly unstable. involving a storage vessel filled with methyl methacrylate. an industrial chemical used widely in plastics manufacturing. When heated. the substance can trigger a “thermal runaway” reaction—an escalating cycle of heat and pressure buildup that can lead to a violent rupture or a full-scale explosion.

After the tank began venting vapors when temperatures spiked, fear grew that thousands of gallons of the chemical could ignite or spill into the surrounding community with little warning. Emergency crews have spent days continuously dousing the vessel with water to stabilize its temperature.

Evacuations began Thursday after officials determined the tank’s escalating condition posed an immediate threat to nearby neighborhoods. Residents were ordered to leave as a precaution while hazardous materials teams assessed the risk and formulated a safe approach strategy.

Even with Sunday’s potential breakthrough, officials said the danger is not over. McGovern and other fire officials reiterated that no residents will be permitted to return until the area is deemed entirely safe.

The overnight discovery came after a specialized Orange County Fire Authority (OCFA) team entered the site for its first visual inspection of the tank. McGovern said the mission was designed to get “eyes on the tank. ” and that the team of subject-matter experts and firefighters successfully identified what appeared to be a crack in the structure. The crew also collected critical data and imagery, which are currently being vetted and validated by technical specialists.

The fire chief called the mission “positive intel,” saying it provided information that could help guide command decisions throughout the day.

Officials also said a faulty valve has left the tank inaccessible, preventing crews from safely draining or neutralizing the chemical from within. That limitation has forced responders to rely on external cooling methods—an ongoing factor that underscores why mass evacuations have remained in place.

At this stage, the key question for technical teams is whether the suspected crack is genuinely easing pressure and whether the tank’s condition is stabilizing.

Fire officials said technical specialists are validating the data and imagery captured overnight. with the primary objective of determining whether the crack is safely relieving internal pressure. If the findings show a positive trend, incident commanders could shift their strategy away from high-risk containment toward controlled mitigation.

That would include reassessing the tank’s structural integrity, determining whether pressure levels are dropping, evaluating whether the area is safe enough for planning repopulation, and deciding whether additional entry operations are needed.

But officials made clear that evacuation orders will remain strictly in place until the site is confirmed secure, and further updates are expected as teams analyze the information to determine whether the incident is moving closer to resolution.

Garden Grove GKN Aerospace OCFA TJ McGovern hazardous materials incident methyl methacrylate chemical tank evacuation orders Orange County Fire Authority