Mokhtar Ben Nasr on Tuesday, adding that in the past week, four bombs made of ammonium nitrate fertilizer had wounded 16 soldiers and police, including two who lost legs and two who lost eyes.

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Ammonium nitrate, a solid fertilizer composed of ammonia and nitrogen, is also a component of explosives widely used in mining.

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Common fertilizer, or ammonium nitrate, which was used in the Oklahoma City bombing, is much harder to regulate.

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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.

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