Oklahoma City Bombing: The Albert P. Murrah Federal Building shows the devastation caused by a fuel and fertilizer truck bomb on April 19, 1995. The blast killed 168 people and injured more than 500. Bob Daemmrich/AFP/Getty Images hide caption

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Mine helmets and painted crosses sat at the entrance to Massey Energy's Upper Big Branch coal mine on April 5, as a memorial to the 29 miners killed there one year earlier. Jeff Gentner/AP hide caption

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The Two-Way

Mine Safety Agency Reports Failures Before Deadly Explosion

But it said its failures did not directly contribute to the blast, which killed 29 coal miners in 2010.

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