Authorities braced for the possibility that a damaged chemical tank in Southern California could leak or explode as an evacuation order continued into the Memorial Day weekend for 50,000 residents with no timeline on when they can return. Firefighters have been spraying the outside of the tank with water hoses in an effort to cool the chemicals heating up inside and prevent an explosion. Lee Zeldin, head of the U.S. Environmental Protection Agency, said Sunday the "most likely scenario" is a "low-volume release," where officials will be able to "monitor, neutralize, and contain the threat." "The Orange County Fire Authority is working to keep the temperature of the tank down. That is very important," he said on CNN.