Evacuation orders issued for 40,000 people in California over explosion threat

The tank contains methyl methacrylate, officials said.

An "emergency hazmat incident" in California has prompted evacuations, with officials warning that a chemical tank at an aerospace facility is in "crisis" and will either fail or explode.

Firefighters initially responded to a leak at an aerospace manufacturing company in Garden Grove on Thursday, for vapor releasing from a 34,000-gallon tank containing methyl methacrylate, according to the Orange County Fire Authority.

Officials updated Friday that there is no active gas leak or plume, but that the tank is "actively in crisis" and unable to be secured. Damage to a valve on the tank has "created additional operational challenges," city officials said.

"There are literally two options left remaining: one, the tank fails and spills a total of about 6- to 7,000 gallons of very bad chemicals into the parking lot in that area. Or two, the tank goes into a thermal runaway and blows up, affecting the tanks that are around them that have fuel or the chemicals in them as well," Orange County Fire Authority Division Chief Craig Covey said in a video update Friday.

"Most importantly, right now, there is no active gas leak, no plume in the area. We are setting up these evacuations in preparation for these two options -- it fails or it blows up," he said.

Authorities have issued evacuation orders for the surrounding area impacting around 40,000 people. Over a dozen schools have temporarily closed, and those adjacent to the evacuation area are canceling outdoor activities "out of an abundance of caution," the Garden Grove Unified School District said.

In an afternoon press briefing, Covey said there are three tanks at the facility. The tank in crisis experienced an increase in temperature and "bulged" on Thursday, he said. An agent used to neutralize the chemical has been ineffective and the chemical is unable to be moved out of the tank due to the broken valves, officials said.

There are no concerns with the other two tanks, Covey said.

Authorities initially issued an evacuation order on Thursday that were lifted when vapor conditions improved. However, evacuation orders were reissued and expanded on Friday due to what police called an "unprecedented" event.

Officials said it is unclear when residents will be able to return to their homes.

"This is highly volatile, it's highly toxic, it's highly flammable," Covey said during the press briefing, while urging people to evacuate. "This is not precautionary. This is gonna happen unless some brilliant guy behind me here figures out how we can mitigate this incident. This thing is gonna fail -- we don't know when."

Methyl methacrylate is an industrial chemical used in plastics and manufacturing and is primarily a respiratory irritant, authorities said. Around 7,000 gallons are estimated to be left in the tank that's in crisis, Covey said.

ABC News has reached out to the aerospace manufacturing company, GKN Aerospace, for comment.

California Gov. Gavin Newsom has been briefed on the incident, his office said.

The California Governor's Office of Emergency Services said it is "closely monitoring the incident in Garden Grove and has deployed personnel to work alongside local partners."

"Please heed all orders from local authorities -- evacuation orders have expanded," it said Friday.

Garden Grove is located about 30 miles southeast of Los Angeles.