The center of the building collapsed like it had no reinforcement. You might expect this if all the steel beams were cut. I don't think you would get that effect with a steel structure. It may occur if a sink hole was under the building. However, if the building was that ready to collapse, there would have been warning signs. The building would show cracks or floor would be tilted. This is not normal.
BTW I am not a civil engineer but I was an aerospace engineer with advanced structures background.