California firefighters will conduct an all-night operation to test the pressure inside a cracked tank at the center of a toxic chemical leak in Orange County, officials said Sunday, as more than 50,000 people remain under evacuation orders.In an incident update posted on X, Orange County Fire Authority Interim Chief TJ McGovern said that crews would conduct the mission overnight to confirm that the "BLEVE threat," or Boiling Liquid Expanding Vapor Explosion, was eliminated. "The BLEVE threat is the worst-case catastrophic event that we've been talking about. We are not there yet; we need to run this operation tonight," McGovern said. He said that an update in the morning would reveal the results of the overnight tank inspection to determine if pressure was released or if there was a vapor buildup inside the tank.In an earlier post, McGovern said that crews discovered a crack in the tank on Saturday night, which could be due to a pressure release. He said that it could alter the strategy as crews search for a solution to the crisis."With this new information, it could change our trajectory and our strategy to this event," he said at the time. "Last night was a successful operation for this emerging incident."The Orange County Fire Authority told CBS LA on Sunday afternoon that multiple cracks existed in the tank. But in a post to X later that night, the agency qualified those reports, saying: "To clarify, there is one known crack on the tank. There is also peeling of weather stripping on the exterior, but this is not an additional crack."