Electrical surges.
Here's another example:
Those flashes on the roof tops could be electrical, but if you look at post 155 and watch the building on the right collapse you can see flashes within that building. Could thermite cord have been used to take down the building?
Evidently there was a construction crew renovating the building. Do we know who the employees of that crew were? Hopefully the Florida police officials can interview the principle witnesses before the FBI gets to them. The sort of catastrophic failure this building suffered is not a result of incompetent construction otherwise it would have fallen years ago. Unless the bedrock beneath the building collapsed this was not a natural event.