Emergency officials in Southern California have lifted evacuation orders for about two-thirds of the roughly 50,000 residents who were told to leave their homes near a damaged chemical tank at the GKN Aerospace Transparency Systems plant in Garden Grove. The decision came after temperatures inside the tank containing 6,000 to 7,000 gallons of methyl methacrylate dropped enough to remove the threat of a major explosion, according to Orange County Fire Authority division chief Craig Covey.
Covey spoke at a news conference on Monday and noted that while the risk of a catastrophic blast has passed, concerns remain about a smaller explosion or fire. “It’s not over yet. We still have work to do,” Covey said. “We still have to mitigate a fire and very small explosion concern, and also a spill potential.” The tank’s interior temperature had cooled to 93 degrees Fahrenheit, down from 100 degrees the previous day, officials reported.
Residents began receiving evacuation orders on Thursday after the tank overheated. By the weekend, approximately 50,000 people in Garden Grove, near Los Angeles, had been directed to leave. About 34,000 of those residents can now return home following the overnight evaluation that showed reduced pressure inside the tank due to a crack discovered on Sunday.
Orange County Health Director Regina Chinsio-Kwong sought to reassure returning residents. “There was no contamination. There were no fumes. There were not vapors that came from this incident,” she said. “There was not a leak. So it should be, you should feel comfortable going home even if you’re across the street from that new zone line.” Exposure to methyl methacrylate can cause respiratory and neurological issues as well as skin and eye irritation, according to the federal Environmental Protection Agency.
Some residents expressed relief mixed with caution. Kim Yen, a retiree who lives two blocks from the plant, said she has been following updates closely. “I am happy and many of us are happy but, still, we are still on our evacuation,” Yen said. She added that she wants confirmation of safety before returning and praised emergency crews, calling them “really our heroes.”
The parking lot at a large park in nearby Fountain Valley filled Monday as evacuees sought shelter or set up tents. Others gathered there to mark Memorial Day. Authorities have not fully defined what a catastrophic explosion would entail but stated that the worst-case scenario is now off the table.
Purdue University engineering professor Andrew Whelton, who has studied environmental contamination, cautioned that temperatures need to drop closer to ambient levels of 60 to 70 degrees Fahrenheit before conditions become significantly safer. He noted that some of the chemical may have already hardened into a stable plastic similar to plexiglass, which could reduce risk inside the tank.
Orange County Supervisor Janet Nguyen said the South Coast Air Quality Management District will monitor air quality for several months while the EPA checks sewer and storm drains. County health officials noted that the chemical is easy to smell and people may notice it over a large area without being harmed.
GKN Aerospace, a British company that manufactures cockpit windows and windshields for military and commercial aircraft, released a statement apologizing for the disruption. “We apologize for the ongoing disruption this incident is causing and our priority remains its safe resolution, so that residents can return to their homes as quickly as possible,” the statement said. The company employs about 16,000 people across 32 sites in 12 countries.
Richard Aboulafia of AeroDynamic Advisory said disruptions at specialized aerospace component facilities can be difficult for the global industry to absorb because supply chains are highly concentrated. “There’s just not a lot of margin in the system,” Aboulafia said. It remained unknown when the Garden Grove plant would reopen.
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 the South Coast Air Quality Management District. Environmental risks persist as crews work to stabilize and drain the remaining material without triggering ignition.