"At this time authorities will not speculate whether the possession of the unregistered destructive device has any connection to the West fertilizer plant explosion, " the U.S. attorney's office for the Western District of Texas said in a release.

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Initial tests showed the device contained ammonium nitrate, the same volatile substance that sparked a massive explosion last month at a fertilizer distribution plant 110 miles north in West, Texas, said Austin fire Lt.

CNN: Austin bomb an amateur job or something more insidious?