A preliminary report on last week's deadly mine explosion in West Virginia suggests the blast may have been preventable.
The report says the cause may have been a buildup of methane gas mixing with coal dust. Such explosions, according to the report, can be prevented when mine operators properly control the levels of methane and coal dust.
But it cautions that the specific cause of the blast at the Upper Big Branch mine is still being determined.
The mine saw a major spike in safety violations last year. The report says the rate of repeated serious violations was nearly 19 times the national rate.
Labor Secretary Hilda Solis presented the report to President Barack Obama and members of West Virginia's congressional delegation.
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