The US Mine Safety and Health Administration has launched a surprise investigation of 57 mines, focusing on ventilation and methane violations, following the West Virginia coal mine explosion that killed 29 people.

Selected for their history of significant and/or repeat MSHA violations regarding problems with ventilation, methane build up and rock dusting, the mines cover ten states, with West Virginia leading the list with 23 mines and Kentucky with 14.

Assistant Secretary of Labor for Mine Safety and Health Joseph Main said the purpose of the inspections is to provide assurance that no imminent dangers, explosions, hazards or other serious health or safety conditions and practices are present at the mines.

Mine enforcement personnel who participated in the inspections examined the mechanised mining units at the selected mines, bleeder systems, belt entries and seals.