T.J. McGovern

What we're doing is we are vetting and validating that information.

With this new information, it could change our trajectory and our strategy to this event.

In a brief video statement, Orange County Fire Chief T.J.

McGovern said that firefighters had conducted a late-night reconnaissance mission.

That might sound bad, but it's actually the least bad scenario.

The tank is filled with 7,000 gallons of a chemical called methyl methacrylate.

It's highly unstable and could explode.

McGovern says the crack may be releasing pressure, which might lessen the chances of that happening.

Still, he says evacuation orders remain in place.

Some 50,000 residents of the city of Garden Grove remain displaced.

Jeff Brumfield, NPR News.