"CHARLESTON, W.Va. -- Mining bits on the longwall machine were worn out, exposing steel shafts that could easily spark when they hit a piece of rock embedded in the coal seam. Key water sprays were missing or inoperable, leaving miners without an important protection against methane ignitions.

Mine operators ignored repeated warnings from their own workers to spread more crushed stone, or rock dust, to prevent coal dust that had built up along miles of underground tunnels from providing fuel for an explosion.

Federal investigators on Wednesday outlined these allegations as the likely factors that combined to produce the huge explosion that killed 29 miners in April 5 at Massey Energy's Upper Big Branch Mine."

Ken Ward Jr. reports for the Charleston Gazette January 19, 2011. [2]