A top federal mine safety official said Tuesday that existing laws and regulations have not been properly enforced but pledged that his agency will now use all its powers after the West Virginia mine disaster that killed 29 people.

Joe Main, the assistant secretary of labor for mine safety and health, told a Senate committee that the Mine Safety and Health Administration will start using its power to immediately shut down mines engaging in unsafe behavior.

Main said the powers have existed for decades but were never used.

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