Orange County firefighters worked through Sunday night to confirm that a crack discovered Saturday on a leaking 7,000-gallon methyl methacrylate tank at GKN Aerospace in Garden Grove is releasing pressure from inside the vessel, a development that could eliminate the catastrophic explosion scenario that has kept 50,000 residents under evacuation orders since Thursday.

If the fissure is in fact venting the tank, Orange County Fire Authority Interim Chief T.J. McGovern told NBC News, "the potential of a BLEVE [boiling liquid expanding vapor explosion] is now off the table." That would not end the incident — crews would still need to cool the tank and deal with the leak — but it would shrink the evacuation footprint and lower the risk of a chain reaction with two adjacent tanks holding the same chemical.

What changed Sunday

The crack was spotted during a visual inspection Saturday night, McGovern said. "With this new information, it could change our trajectory and our strategy to this event," he told reporters. The Orange County Fire Authority on Sunday quashed earlier reports of multiple cracks, saying there is one known fissure and that peeling on the tank's exterior is weather stripping loosened by the constant water hose, not a second break.

McGovern said the overnight operation was an "all-night mission in order to confirm that the pressure in the tank has been released" and that the BLEVE threat is eliminated. He cautioned the worst case has not yet been ruled out: "We are not there yet." Air monitoring by the South Coast Air Quality Management District and 24 Environmental Protection Agency stationary monitors showed no chemical release as of Sunday night.

The investigation

Orange County District Attorney Todd Spitzer's office has opened a criminal investigation into the tank's failure and on Saturday opened an anonymous tip line for GKN Aerospace employees. "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. The X-Law Group and Presidio Law Firm filed a class-action lawsuit against GKN on behalf of evacuated residents.

Gov. Gavin Newsom, who declared a state of emergency Saturday, asked President Trump on Sunday to issue a federal emergency declaration that would unlock FEMA assistance. Democratic Sens. Alex Padilla and Adam Schiff and Rep. Derek Tran co-signed the request. The White House had not responded by Sunday night.

Counterpoint

All four body-tier sources today are lean-left outlets — CBS News and NBC News — relying on the same Orange County Fire Authority briefings. A substantive industry or facility-operator account of how the tank reached thermal runaway, and a response from GKN Aerospace beyond its brief statement that it is working "round the clock," were not publicly available at press time. Orange County GOP officials, who represent much of the evacuation zone, had likewise not issued public comment on the DA probe or the company's maintenance record.

McGovern said an update on the overnight pressure test was expected Monday morning. Officials have set no timeline for lifting evacuation orders.