Only 3 Things Could Have Caused Texas Blast

Investigators working in the remnants of an exploded Texas fertilizer plant sifted by hand through untold grains of corn, moved tons of debris, and conducted more than 400 interviews while searching for the missing piece to solve what many officials compared to an extraordinary puzzle. One month after a fire triggered a massive blast killing 15 people, officials yesterday had to declare the cause of the blaze as "undetermined."

Investigators narrowed the number of possible causes to three: a problem with one of the plant's electrical systems, a battery-powered golf cart, and a criminal act. They ruled out a wide number of others, from a rail car on site loaded with fertilizer to someone smoking. They also ruled out the possibility that the blast was an act of terror, but not that it was a crime. The blast was actually two explosions: a small one that occurred about 20 minutes after the fire was reported, followed by a larger one a split second later, a fire spokesperson said. About 28 to 34 tons of ammonium nitrate stored in the plant exploded. (More Texas stories.)