May 24 (UPI) — Tens of thousands of Orange County, Calif., residents remained evacuated Sunday as officials nervously watched the condition of a failing, 34,000-gallon tank containing dangerous chemicals.

Orange County fire officials said a visual inspection of the overheated tank in Garden Grove, Calif., late Saturday showed it has potentially developed a crack, which could reduce the possibility of a catastrophic explosion but increase the likelihood of a massive spill of liquid methyl metacrylate.

“Right now, we’re vetting and validating that information,” Orange County Fire Authority Interim Chief T.J. McGovern said in a video update of the tense situation at the GKN Aerospace facility, located about 33 miles southeast of downtown Los Angeles.

The discovery of a potential crack in the tank “could change the trajectory and our strategy for this event,” he said.

A crack in the tank “may avoid the two concerns that we all had,” Calif. State Sen. Tom Umberg told KCBS-TV. “One was an explosion, the other was a leak of liquid material vaporizing into a toxic fume, a toxic plume.”

California Gov. Gavin Newsom on Sunday transmitted a request to President Donald Trump to declare a federal emergency in support ongoing response operations in Orange County.

The request came a day after the governor’s proclamation of a state of emergency as officials raised the alarm about the possibility of a catastrophic explosion and a major release of toxins.

“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.”

The state says it has already activated its emergency operations center, deployed mutual aid resources and has pre-positioned emergency personnel — including fire, law enforcement and medical teams — in the area around the GKN Aerospace facility, which is just 7 miles west of the Disneyland amusement park.

Nearly 50,000 Orange County residents remained under mandatory evacuation orders on Sunday as an interagency response team eyed the malfunctioning tank, which holds methyl methacrylate, or MMA, a flammable, toxic and highly volatile substance used in the production of acrylic plastics.

Residents were evacuated Friday after a chemical vapor leak was spotted coming from the tank, which has a malfunctioning valve and is unable to be neutralized. Officials say the valve has seized due to a chemical reaction with the MMA.

Water cooling by firefighters has so far kept the tank’s temperature stable and no injuries have been reported.

No unusual readings of toxic material have yet been detected in the area.

The evacuation zone is in a densely populated area of Orange County and has multiple public facilities including schools, hospitals, nursing homes, fire and law enforcement stations.

A unified command has been established between Orange County Fire Authority, Garden Grove Police Department and Orange County Health Care Agency to deal with the emergency.