Emergency crews in Southern California worked through the night in a tense effort to prevent a potentially catastrophic chemical explosion at an aerospace facility in Orange County, where rising temperatures inside a failing tank prompted widespread evacuations and a state of emergency declaration from Gavin Newsom.

Officials said more than 40,000 residents were evacuated as firefighters and hazardous materials teams raced to stabilize the dangerous situation.

According to Orange County Fire Authority Incident Commander Greg Covey, crews entered the high-risk area overnight to manually inspect the failing chemical tank after cooling water made drone monitoring impossible. The inspection revealed the internal temperature had climbed to 90 degrees Fahrenheit — steadily increasing about one degree per hour since Friday morning.

Emergency officials warned that the situation remains extremely dangerous because the overheated tank contains thousands of gallons of volatile chemicals. Authorities fear two possible worst-case scenarios: the tank could rupture and release toxic chemicals into the surrounding area, or it could experience a “thermal runaway” reaction and explode.

Fire officials said an explosion could trigger a chain reaction involving nearby fuel and chemical storage tanks, dramatically escalating the crisis.

As part of the overnight emergency operation, hazardous materials specialists and chemists focused on neutralizing a nearby 15,000-gallon chemical tank in hopes of reducing the risk of a larger explosion if the primary tank fails.

At the same time, crews continued flooding the overheating tank with large amounts of water in an effort to cool and stabilize the chemical reaction. Officials described the strategy as an attempt to slowly harden the material from the outside inward, similar to the way ice forms.

Authorities said they are also preparing for the possibility of a major spill. Emergency teams have constructed containment barriers and diversion systems designed to redirect chemicals away from storm drains, waterways, and the Pacific Ocean in order to avoid a major environmental disaster.

“Letting this thing explode is simply not an option,” Covey said during a briefing, noting that experts from across the country are now assisting with the emergency response.

The growing danger prompted Gavin Newsom to officially declare a state of emergency Saturday, allowing California agencies to deploy additional resources and emergency support to Orange County.

In a public statement, Newsom said state emergency teams had already been mobilized for more than 24 hours and were working closely with local officials to protect residents and stabilize the situation.

Firefighters, hazmat specialists, environmental officials, and law enforcement agencies remain on scene as crews continue working to prevent the chemical crisis from escalating further.