GARDEN GROVE, CALIFORNIA — Authorities worked through the Memorial Day weekend to contain a damaged chemical storage tank at a GKN Aerospace facility in Garden Grove, California, that posed a threat of a leak or explosion. More than 50,000 residents in the area west of Anaheim were placed under an evacuation order, though Disneyland's two theme parks were not included.

The tank held between 6,000 and 7,000 gallons of methyl methacrylate, a flammable, colorless liquid used in the production of resins, plastics and plastic dentures, and regulated by the federal government as a hazardous substance. The tank overheated last week and began leaking vapors into the air around the Orange County city. Officials said the drainage valves on the tank were not functioning, and that without intervention there could be either a large chemical spill or an explosion.

Firefighters sprayed the tank with water to cool the chemicals, focusing on keeping the temperature under 85 degrees Fahrenheit (29.4 degrees Celsius) to relieve pressure. If the tank's temperature rises, the methyl methacrylate converts from a liquid to a gas, increasing pressure and the risk of an explosion that could ignite other tanks at the site.

"The most likely scenario is a low-volume release of the tank's contents, so officials can monitor, neutralize, and contain the threat." Environmental Protection Agency chief Lee Zeldin said a low-volume and controlled release would allow officials to monitor the chemical and relieve pressure on the tank.

According to the EPA, methyl methacrylate can irritate the lungs, eyes and skin, and in high doses can cause reduced lung function, dizziness and memory problems. Prolonged exposure can cause serious respiratory problems or render a person unconscious. A blast releasing the chemical into the air would send it into a wider area and could create vapors that are hazardous to inhale, according to Dr. Regina Chinsio-Kwong, Orange County's top health officer.

"Inhaling the vapor could cause irritation to the eyes, nose and lungs and may cause a sore throat, burning eyes and dizziness." Chinsio-Kwong said the chemical has a fruity odor, but smelling it does not mean a person will have health impacts, and that people outside the evacuation zone do not need to worry about health effects.

Air monitoring tests found that air pollution around the evacuation zone was within normal limits, and no injuries have been reported. Officials said Sunday the tank may have cracked, potentially lowering the risk of an explosion. Emergency crews spotted a possible crack overnight, Orange County Fire Authority Capt. Wayhowe Huang said, adding that despite the crack, the tank did not appear to be releasing any toxic chemical into the atmosphere. GKN Aerospace continued to work with local authorities.