From what I understand, I believe they were testing the turbines with the natural gas and after they completed the testing, as they were "blowing down" the lines filled with natural gas - that's when the explosion happened... The only silver lining is the fact that there were probably less than 100 people their today being that it was a Sunday, and they would be testing which is what went wrong, and I can only guess that we'll be reading more about the specifics as to what actually caused the explosion very soon.

Unfortunately, there is a confirmed 2 fatalities so far, and there's quite a few injuries, but the real concern right now is the fact that there are quite a few people that have yet to be accounted for. :(

Respectfully,
Henry