This is an interesting read if anyone is interested.
The Sustainability of the Controlled Demolition Hypothesis for the Destruction of the Twin Towers
Page four, 3rd paragraph: "Steel can only be melted in the controlled environment of a blast furnace or with the use of incendiaries."
4th paragraph: "There is very credible witness testimony of seeing, hearing and feeling explosions, in many areas of the towers, both before and during the collapses. This testimony can be found in the Oral Histories of the 503 NYC firefighters and emergency personnel, who were on the scene that day and survived."
Here's a list of the unedited
Oral Histories the author is referring to.