California crews prepare overnight operation as toxic leak keeps 50,000-plus under evacuation orders

Firefighters in California, US, were preparing Sunday for an overnight operation to assess pressure levels inside a damaged chemical storage tank at the center of a toxic leak in Orange County, as evacuation orders affecting more than 50,000 residents remained in effect, officials said.

TJ McGovern, interim chief of the Orange County Fire Authority (OCFA), said emergency crews would carry out overnight operations aimed at determining whether the risk of a Boiling Liquid Expanding Vapor Explosion, known as a BLEVE, had been eliminated.

“The BLEVE threat is the worst-case catastrophic event that we’ve been talking about. We are not there yet; we need to run this operation tonight,” McGovern said in an update posted on the US social media platform X.

He said officials would review results in the morning to determine whether internal pressure had been safely released or whether dangerous vapor accumulation remained inside the tank.

Authorities said the incident began at GKN Aerospace in Garden Grove, where approximately 7,000 gallons of methyl methacrylate are stored.

Officials said they first identified a crack in the tank Saturday night, a development they said could alter their response strategy.

“With this new information, it could change our trajectory and our strategy to this event,” McGovern said.

“Last night was a successful operation for this emerging incident.”

Fire officials later clarified that investigators had identified one confirmed crack along with damage to exterior weather stripping.

“To clarify, there is one known crack on the tank,” the Orange County Fire Authority said, adding that peeling material observed on the structure was caused by water exposure during firefighting operations.

OCFA Public Information Officer Wayhowe Huang said continuous water application may have created confusion regarding additional structural damage.

The crisis, now entering its fourth day, remains unstable as elevated temperatures persist inside the tank.

Firefighters said readings exceeded 100 degrees Celsius, significantly above safe limits for the chemical involved.

“It’s very unsafe. We as firefighters, hazmat team, and all the experts, have to be very methodical when they approach this scene. It’s very calculated, there’s a lot of risk involved,” said OCFA Fire Captain Brian Yau.

Officials said operations were being carried out with extreme caution because any additional pressure buildup could trigger a catastrophic event.

Emergency crews continue monitoring conditions around the clock while maintaining evacuation zones across affected neighborhoods.

Gavin Newsom has requested a federal emergency declaration from US President Donald Trump, a move that would allow assistance from Federal Emergency Management Agency (FEMA) and release additional funding.

“California doesn’t wait for disaster to unfold, we act early to protect lives and communities,” Newsom said, emphasizing coordination with federal and local authorities.

In a joint letter, US Senators Alex Padilla and Adam Schiff, along with Representative Derek Tran, urged approval of the request.

“The severity of this disaster requires additional coordination and federal support,” they wrote.

Officials said more than 785 state and local responders remain deployed as authorities continue efforts to stabilize the tank and prevent further escalation.