Crews monitor chemical tank temperatures every 10 minutes as pressure builds with relief valves failing
Drones were checking the chemical tank’s temperature every 10 minutes, watching for spikes as pressure inside the vessel continued to build, The Independent reported. Crews were simultaneously planning how to stop any potential leak from spreading into nearby waterways or the ocean. [1]
Firefighters focused on one immediate goal: cooling the methyl methacrylate inside the tank so it would not leak or explode. [1] Officials said the tank’s pressure relief valves were no longer working, and that pressure was rising as the chemical converted from liquid to gas. [1]
Division chief Craig Covey said the valves were broken or “gummed up,” blocking efforts to remove the chemical or relieve the pressure on the tank. [1] The conditions have left crews monitoring the tank closely as they weigh how to keep the situation from escalating. [1]
This is the latest chapter in an ongoing Southern California incident that has kept tens of thousands of residents evacuated since 2026-05-23, as crews work to prevent the tank from exploding amid rising temperatures. A state of emergency was declared on 2026-05-24, and the Orange County District Attorney launched an investigation into the aerospace company responsible for the leak. [1]
Andrew Whelton described the worst-case scenario as an explosion that could spread the chemical over a broad area and send shrapnel flying. [1] If cooling proves impossible, he said it would be best if the tank sprang a leak so the chemical could be mostly contained. [1]
Timeline· Developing
More than 40,000 people in Southern California remain evacuated as crews urgently work to prevent the hazardous chemical tank in Orange County from exploding amid rising temperatures reported by the Orange County Fire Authority, with Governor Gavin Newsom maintaining a state of emergency and the OC District Attorney investigating the aerospace company responsible for the chemical tank leak amid ongoing uncertainty about evacuees' safe return.
Chemical leak prompts initial mass evacuations
A chemical leak in Southern California led officials to order evacuations affecting roughly 20,000 people as responders warned the storage tank was compromised and could fail. Residents were moved to shelters while authorities assessed the hazard.
- Evacuations expand; streets and shelters emptied
Evacuation orders widened, with reports indicating up to 40,000 people were under orders or advised to leave and shelters filled as neighborhoods emptied amid ongoing fears about the leaking tank. Local officials described large-scale displacement and sheltering operations across Orange County.
Governor declares state of emergency
Gov. Gavin Newsom declared a state of emergency over the chemical incident to mobilize state resources and support local response efforts as the situation escalated. The declaration aimed to speed assistance to affected communities and responders.
- Officials warn tank heating risks explosion
Fire authorities reported rising temperatures in the chemical tank and warned it was at risk of failing or exploding, prompting continued or expanded evacuation orders affecting tens of thousands. Officials characterized the tank's condition as critical and hazardous.
State races to prevent explosion with novel fixes
California authorities pursued urgent and unconventional measures to cool or stabilize the heating tank, describing a race to prevent an explosion while emergency teams assessed technical options. The efforts underscored the complexity and immediacy of the threat.
Local prosecutor opens investigation into company
The Orange County district attorney opened an investigation into the aerospace company responsible for the chemical tank, signaling potential legal and regulatory scrutiny over the cause of the leak and management of the tank. The probe followed mounting public concern and emergency actions.
Related Coverage (2)
Garden Grove chemical tank leak forces 40,000 evacuations as fire chief warns of spill or explosion risk
Officials warned the leaking tank posed two main dangers: it could fail and spill chemicals or enter thermal runaway and explode, potentially affecting nearby fuel and chemical tanks.
Officials cool damaged chemical tank as planners weigh rupture-or-explosion scenarios
Fire officials planned for two outcomes at a damaged chemical tank: a rupture and spill, or an explosion, Orange County Fire Authority division chief Craig Covey said.
Published May 24, 2026
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