Well there are many reports from firefighters and other people who were there that they heard loud explosions just as the first tower went down.
I'd say they heard a great many things they couldn't identify..many of which would be a result of thousands of tons of debris crashing down as well
as the steel structure buckling under the redistribution of the load due to the intense heat and pressure as well as the missing members destroyed
upon impact.
Many people claim that the towers wouldn't have fallen like they did unless demolitions had been used.
Not everyone has had the training and education in engineering and construction to understand the properties of building materials and their reactions
to such a blunt strike. Thos of us who do not only understand why they fell but can't figure out how the heck they stood as long as they did after
the main support structure had been severed.
One theory is that the masts that ran from top, to bottom of the towers were severed at the bottom by explosives.
Now, that is a partial true statement. The support structure was severed by an explosion is each case. This removal of supporting members on each
side made the remaining bear more load than they were designed. This extreme and fast change in pressure along with the heat of the burning fuel
weakened those remaining members. Once they failed and the top floors impacted the bottom floors, immediate failure was unavoidable throughout the
structure.
