Officials battling a dangerous chemical leak in Orange County said Sunday they may have found a breakthrough after crews discovered what could be a pressure-relieving crack in the tank at the center of the crisis.

Orange County Fire Authority Interim Chief TJ McGovern said the finding still needs to be confirmed, but noted it could significantly change the response strategy. “With this new information, it could change our trajectory and our strategy to this event,” he said. “Last night was a successful operation for this emerging incident.”

The emergency entered its fourth day Sunday as a leaking tank holding roughly 7,000 gallons of methyl methacrylate continued to threaten surrounding communities at the GKN Aerospace facility in Garden Grove. Nearly 50,000 residents remain under evacuation orders.

California Governor Gavin Newsom declared a state of emergency Saturday and requested an Emergency Declaration from President Donald Trump, which would activate FEMA assistance and unlock federal resources.

“California doesn’t wait for disaster to unfold, we act early to protect lives and communities,” Newsom said. “Working together with our local and federal partners, we’re strengthening our ability to respond quickly and effectively in Garden Grove and across the surrounding communities and ensuring that first responders have the resources they need to keep people safe.”

Fire officials warned earlier in the crisis that the tank could either rupture and spill thousands of gallons of hazardous chemicals or enter a “thermal runaway” reaction that could trigger a catastrophic explosion affecting nearby fuel and chemical tanks.

“There are literally two options left remaining: One, the tank fails and spills a total of about [6,000] to 7,000 gallons of very bad chemicals into the parking lot and that area,” OCFA Division Chief Craig Covey said Friday. “Or two, the tank goes into a thermal runaway and blows up, affecting the tanks that are around it that have fuel or chemicals in them as well.”

Officials now believe a possible third option may exist after signs emerged that pressure inside the tank could be releasing naturally. State Sen. Tom Umberg called the development encouraging, saying, “That may avoid the two concerns that we all had. One was an explosion, the other was a leak of liquid material vaporizing into a toxic fume, a toxic plume.”

Covey stressed that officials are determined to avoid disaster. “Letting this thing just fail and blow up is unacceptable to us,” he said. “Our goal is to find something and not allow that to happen.”

Authorities have brought in outside experts from across the country while investigators examine what caused the failure. Orange County District Attorney Todd Spitzer announced a formal investigation Saturday and urged employees and whistleblowers connected to GKN Aerospace to come forward.

“I am indicating to employees who work at GKN: If you want to come forward and you want to be interviewed and you want to tell us what you know, now is the time,” Spitzer said. “When we launch an investigation, and we get to the bottom of what happened and why the system failed, if you haven’t come forward, you’re not gonna be treated the same as if you come forward early and you tell us what you know.”

Spitzer described the situation as “irresponsible” and “horrific,” while evacuated residents have already filed a class-action lawsuit against GKN Aerospace over the disruption and possible health risks.

The company said Sunday it is “working round the clock to mitigate the risk of a leak.”

“We are acutely aware of the uncertainty this incident is causing and sincerely apologise for the ongoing disruption to the local community,” the statement reads. “Our priority remains the safe resolution of this incident, so that residents can return to their homes as quickly as possible.”

Health experts warned methyl methacrylate is a highly flammable chemical capable of triggering a runaway reaction. USC chemistry professor Elias Picazo explained: “In an uncontrolled environment with a leak, you can potentially have a lot in the atmosphere, and any flash or spark or even temperature can cause what is known as a runaway reaction.”

He added, “Heat initiates the reaction, but the reaction releases heat, and so you get what we call ‘runaway,’ where it’s uncontrolled. It can lead to, yes, fires, explosions, where pressure really builds up very quickly.”

Despite fears of a catastrophic blast, environmental monitoring has so far detected no dangerous gas releases outside the evacuation zone. Officials continue conducting air monitoring around the clock while drones track the tank’s temperature.