Firefighters warned Saturday that a tank of toxic chemicals in California is heating up, adding to fears of a catastrophic explosion that has already forced tens of thousands of Californians to evacuate. About 40,000 residents were ordered to leave their homes in the Garden Grove area of Orange County, southeast of Los Angeles, on Friday after the tank began to leak, sending fumes over a heavily populated area. The tank contains 7,000 gallons (26,000 liters) of methyl methacrylate, a volatile and flammable liquid used to make plastics, with firefighters warning the situation was serious. Orange County Fire Authority Incident Commander Craig Covey said Saturday morning that an emergency team had ventured into the area overnight, seeking to neutralize the "explosive potential" posed by an additional 15,000-gallon tank nearby should the 7,000-gallon tank blow up, and were then able to view the temperature gauge on the 7,000-gallon tank. "Unfortunately, I do have to report that the temperature was 90 degrees (Fahrenheit; 32C). Yesterday morning, it was 77 degrees when we backed out. It's been averaging about a degree an hour increasing, so that's the bad news," he said in a short video posted on social media. He said firefighters are seeking ways to cool the tank. Aerial footage filmed by local TV stations on Friday showed jets of water being sprayed at the tank, which has a capacity of 34,000 gallons. "The primary focus is the tanks," Covey said during a Saturday evening press conference. "We're continuing to keep them cool and monitor them." A blast zone map released by the Orange County Fire Authority showed areas within about 1,100 feet (335 meters) of the tank would sustain severe damage in the event of an explosion, and about the same distance from that radius could expereince light damage. On Friday, authorities described the tank exploding or rupturing as the only possible outcomes, but on Saturday Covey said: "Letting this thing just fail and blow up is unacceptable." "Our goal is to find something and not allow that to happen, not to let it damage our community, not let it damage our environment." He added that residents had followed directions to evacuate and the only people at risk now were the emergency responders. 'Diking and damming' Orange County Health Officer Regina Chinsio-Kwong said Friday the large exclusion zone around the tank was a necessary precaution. "If it does explode and there is a vapor, you are all safe as long as you are out of the zone that was determined to be an evacuation zone," she said. No injuries had been reported by Friday evening, and there was no immediate indication as to what caused the leak, which was initially reported on Thursday. Responders were working to put containment barriers in place to prevent any spilled material from reaching storm drains or river channels that funnel into the ocean. The US Environmental Protection Agency says methyl methacrylate is irritating to the skin, eyes, and mucous membranes in humans. "Respiratory effects have been reported in humans following acute (short-term) and chronic (long-term) inhalation exposures," a fact sheet on the agency's website says. "Neurological symptoms have also been reported in humans following acute exposure." (Except for the headline this story has not been edited by Firstpost staff.)