WEST, Texas -- Explosion investigators spent their first full day Friday exploring the scene and searching for clues as to what triggered the devastating blast Wednesday night in West, Texas.
The suspected culprit at this early stage is a highly-explosive fertilizer, ammonium nitrate, which was being stored in large quantities on site.
State and federal investigators Friday could be seen combing through the debris at ground zero. They inspected a huge crater - several feet deep - where a large building once stood, containing an assortment of fertilizers.
Of greatest concern was up to 270 tons of ammonium nitrate, which the owner had properly reported to state authorities. Reporting the existence of ammonium nitrate is important because of the chemical's well-known potential to explode.
It was the main ingredient used to bomb the federal building in Oklahoma City in 1995. Since then, new federal laws make it difficult to find out where ammonium nitrate is even sold.
Since Thursday, News 8 has identified a half-dozen similar fertilizer storage facilities in North Texas that stock ammonium nitrate, like one we found in Itasca, Texas, 20 miles north of the explosion in West.
By itself, when properly ventilated, the chemical is considered safe. So what caused the chemical to explode in West?
Explosion and pipeline safety expert Don Deaver said the likely trigger is the fire that raged just feet away from the storage building on Wednesday night.
"And if you have ammonium nitrate inside of a building that comes into contact with this type of heat, you are going to have an explosion,” Deaver said. “I mean, it’s the perfect storm for an explosion. You've got the ignition source, you've got the heat, and the hotter it is the more explosive it is."
State chemical storage reports on file with the Texas Department of State Health Services indicate that the explosive chemical was on site and had been for the past year. Deaver said the key question now is why wasn't more done to prevent a massive explosion.
"What was done to keep it keep it from happening?” Deaver asked. “What safety precautions were in place? What type of interactions and communications were there with the fire fighters?"
News 8 wanted to know that answer, too. But federal and state regulators have declined to comment to News 8 regarding regulations governing the handling of ammonium nitrate and how the public could be so oblivious to its devastating potential.