I looked into Underwriter Laboratories, as the work that they do is both interesting and important in mitigating future disasters.
The article did not give a definitive answer as to the decided cause of the towers collapse, so I researched the prominent theories. There still exists some controversy on the subject but it is largely believed that a combination of the direction the plane faced upon impact, which allowed the keel beam to destroy several support columns of the building, and the heat form the fire causing thermal expansion of the remaining steel reinforcements, overtaxed the supports which led to a systematic failure of supports on each lower floor.
Finally, I looked at the legal changes after 9/11 to see if there were any laws put into place defining the responsibility and authority of government agencies in the aftermath of a disaster. The laws passed directly in response to 9/11 however only seem to be relating to search, seizure, and detention of suspected terrorists.