This April 18, 2013 file photo shows an aerial view of the remains of a fertilizer plant and an apartment complex to the left, destroyed by an explosion in West, Texas.  The government has failed to inspect virtually all of the chemical facilities that it considers to be at high risk for a terror attack, numbering in the thousands, and has underestimated the threat to densely populated cities, congressional investigators say.  (AP Photo/Tony Gutierrez, File)
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