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Authorities in Southern California are bracing for the possibility that a volatile chemical tank could either rupture or explode, as emergency crews worked through the night on what officials described as an unprecedented hazmat crisis that has forced an estimated 40,000 people from their homes.
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Orange County Fire Authority incident commander Craig Covey said firefighters and chemical experts made a risky overnight attempt to stabilize the situation at an aerospace manufacturing facility in Garden Grove, sending crews close enough to inspect the tank directly.
What they found was troubling: The tank’s internal temperature — which could not be measured by drone — had climbed from 77 degrees to 90 degrees overnight and was continuing to rise by roughly 1 degree per hour, Covey said in an update Saturday morning. He previously said the chemical’s “happy place” is at 50 degrees.
“Letting this thing just fail and blow up is unacceptable to us,” he said. “We’re going to do everything we can to mitigate this, protect your residences, protect our environment, and get you back home.”
Gov. Gavin Newsom on Saturday declared a state of emergency in Orange County in response to the crisis, directing state agencies to support responders and making state-owned properties and fairgrounds available as potential shelters.
Crews are now simultaneously preparing for three scenarios: the tank rupturing and spilling toxic chemicals, the tank exploding, or a slower “curing” process in which heavy water cooling could reduce pressure buildup enough to prevent a disastrous explosion.
Covey said firefighters are also developing contingency plans for a possible environmental disaster if the tank spills, including efforts to divert the chemical away from storm drains, river channels and ultimately the ocean.
The fire authority’s division chief Nick Freeman said emergency planners mapped separate zones for potential blast impacts, structural damage, flammability risks and hazardous vapor exposure if the tank fails.
Orange County Health Officer Dr. Regina Chinsio-Kwong tried reassured residents outside the evacuation area, saying those beyond the designated zone were not believed to face health risks and did not need masks.
The 7,000-gallon tank contains methyl methacrylate, a toxic chemical used to manufacture resins and plastics, including Plexiglass.
“MMA does have a very strong fruity odor,” she said Saturday. “Smelling it doesn’t mean that it will have health impacts.”
Chinsio-Kwong previously called the emergency unprecedented.
“This is a unique situation,” she told reporters. “We don’t have information of a similar situation where this happened.”
Firefighters also attempted overnight to neutralize an additional 15,000-gallon tank nearby to reduce the overall risk at the site, Covey said.
Crews have been cooling the tank for hours using a sprinkler system and unmanned hose lines in hopes of slowing the chemical reaction inside.
Covey said officials now believe the water may be helping slow the “curing” process, comparing it to an ice cube freezing from the outside inward.
“We are not giving up,” Covey said. “We are not accepting the fact that we just have to let this thing fail. We’re going to try to find a solution.”
The evacuation zone includes parts of of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster. Garden Grove is about 35 miles southeast of downtown Los Angeles.
Additional evacuation shelters opened Saturday morning.
No injuries have been reported and officials said air quality monitors have not detected methyl methacrylate in the air.
Major Southern California attractions remained open Saturday as officials monitored the situation. Knott’s Berry Farm, located about 6 miles north of the site, said it has not been impacted and was coordinating with fire officials.
“The safety and wellbeing of our guests and team members is a cornerstone of our business,” a park spokesperson told NBC News. “We are working closely with our partners at the Orange County Fire Authority to actively monitor the situation. At this time, the park has not been impacted.”
Disneyland Resort, about 7 miles northeast of the facility, also remained open, according to a Disneyland official, who said the resort was actively monitoring the emergency and supporting employees affected by the evacuation orders.
The California Governor’s Office of Emergency Services said it activated the State Operations Center to support the local response.
According to the U.S. Environmental Protection Agency, methyl methacrylate can cause lung and skin irritation, headaches, coughing and wheezing, and has been suggested but not proven as a possible cause of colon and rectal cancers.
Garden Grove Police Chief Amir El-Farra told reporters that the evacuation zone includes about 40,000 residents.
The EPA is supporting local authorities with air monitoring. A spokesperson said OCFA is the lead agency handling the emergency.
Authorities first responded to reports of a “vapor release” from multiple chemical storage tanks at the facility on the 12100 block of Western Avenue in Garden Grove at about 3:22 p.m. Thursday, the OCFA said in a statement.
A spokesperson for the manufacturer on site, GKN Aerospace, said by email: “The situation at our Garden Grove site remains ongoing, and we are fully focused on working with emergency services and the relevant authorities to ensure the safety of our employees and the local community.”
Dennis Romero is a breaking news reporter for NBC News Digital.
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