A new map has revealed the potential blast radius of a chemical tank on the verge of exploding at a California aerospace facility.

More than 40,000 people have already evacuated the area around the city of Garden Grove after officials reported a toxic leak Thursday afternoon.

The 34,000-gallon tank at the GKN Aerospace facility contains methyl methacrylate (MMA), a highly flammable chemical used to make acrylic plastics.

Officials have been battling to contain the leak but have so far been unsuccessful and warned it will now only be a matter of time before it 'ruptures or explodes.' 

'This is not precautionary. This thing is going to fail, and we don't know when,' Orange County Fire Authority Division Chief Craig Covey said. 

On Saturday, officials released a map showing the potential blast zones should the tank explode, along with nearby areas that could be affected from the impact.

The severe damage blast zone consists of the innermost circle closest to the tank, representing areas where 'severe structural damage and significant harm' are expected. 

Just outside are the moderate damage blast zone and light blast damage zone, where officials predict more limited structural damage and potential harm, though less severe.

At the center of a map is a dark red oval indicating where flammable conditions could spark a fire or flash fire. 

The orange oval, officials said, marks areas immediately dangerous to life and health,  where exposure could 'cause injury if anyone inhales or is impacted by the product in question.'

Orange County Fire Authority Division Chief Nick Freeman warned that the highly toxic chemical poses severe health risks to people and animals in this area, particularly to the respiratory system.

'Respiratory is our primary concern, so it’s a respiratory irritant,' he told KTLA. 

'It can start off very mild but it can progress to a point where you would probably require hospitalization, if not more.'

Orange County Health Officer Dr Regina Chinsio-Kwong added that inhaling the vapor could cause dizziness, nausea, and, at high levels, severe respiratory distress. 

'When you have limited, short-term exposure, meaning maybe you inhaled some of the vapor, it can cause significant irritation in the lungs, the nasal passages,' she told the outlet.

The final and largest area - the yellow oval zone - is considered a non-hazardous zone, marking the odor threshold. 

Freeman said: 'This product has a very low odor threshold and can be smelled very easily, so that's why the area is very large, but it is non-hazardous at that level.'

Chinsio-Kwong explained that the chemical has a strong, fruity scent, but noted that 'smelling it doesn’t mean it will have health impacts.'

'We know that when you smell it, you don’t typically have symptoms and when you actually measure the levels in the air, it doesn’t mean it’s dangerous,' she told KTLA. 

'But again, if you are not in the evacuation zones, we do not expect any health impacts.'

She also stressed that the evacuation zone was based on a worst-case scenario, and urged all residents to stay away from evacuated areas. 

'If you are not in the evacuation zone, you do not need to worry,' she added, noting that masks are not necessary. 'If you remain in the evacuation zone, that’s where your risk increases.'

'We have taken all the things into consideration and the map and blast zone map is just thinking about the worst case scenario. If you were told to evacuate, please evacuate because we’re trying to keep in mind your safety.'

Forty-thousand to 50,000 people have already fled their homes amid what officials are describing as an 'unprecedented industrial disaster' rapidly heading toward catastrophe. 

Late Saturday, Orange County prosecutors announced an investigation into the aerospace company, with District Attorney Todd Spitzer calling the situation 'horrific.'

Spitzer revealed that the investigation will examine both GKN Aerospace and the overheating chemical tank that triggered the mass evacuation.

In an interview with the Orange County Register, he argued that any responsible contractor working with chemicals would avoid such grave failures. 

'It is certainly unreasonable to believe that any responsible defense contractor that makes aircraft windows and uses in the process would have failures of its cooling system that maintains the safety level of its chemicals,' Spitzer said.

'There will be incredible costs associated with this situation and I’m going to be front and center in making sure people are made whole,' he added.

The DA’s office has also opened a hotline for workers or insiders with information about what went wrong at the plant.

Prosecutors are now looking into facility operations, including maintenance practices, and whether prior warning signs were ignored. 

Tipsters were urged to contact the OCDA anonymous hotline, email prosecutors, or submit information online.  

Regarding the tank, officials said only two outcomes remain. 

'One, it fails and cracks and all the product leaks out onto the ground,' Chief Covey said. 'The other option that was told to us is that it blows up.' 

The crisis unfolded at the major manufacturer of engine structures and aerospace components for commercial and military aircraft at around 3.30pm Thursday.

Firefighters first responded after vapors began escaping from the massive storage tank at the company's Garden Grove facility. 

Officials said the tank’s temperature rose, triggering a relief valve designed to safely release pressure. 

At first, crews believed they had stabilized the situation after deploying cooling measures and using water systems to lower the temperature, but the situation deteriorated again that evening and overnight.

By early Friday morning, officials realized a damaged valve on the compromised tank made it impossible to safely remove or neutralize the chemicals inside.

Authorities warned that if the tank ruptures, it could spill 6,000 to 7,000 gallons of hazardous chemicals, or explode and trigger fires in nearby tanks containing fuel and other substances.

Sand barriers and containment systems were erected around the facility on Friday in hopes of preventing chemicals from reaching storm drains, river channels and eventually the ocean if the tank bursts.

Drones were also deployed overhead to monitor the tank's temperature as hazmat crews searched desperately for a solution. 

Covey said emergency officials had contacted specialists 'all over the state and country' looking for what he described as 'out of the box' ideas to prevent disaster. 

Some residents described frantically trying to decide what belongings they could carry with them while uncertain whether they would be allowed to return home anytime soon. 

Westminster resident Britney Pham told the Orange County Register she struggled to decide whether to bring an urn containing her late sister's ashes.

'Should we be getting everything that we think is important, or do we just grab what's basically essential to live for the next couple of days?' she said.

The crisis also forced widespread closures across the region.

More than a dozen schools shut down operations while others canceled outdoor activities 'out of an abundance of caution,' according to the Garden Grove Unified School District.