Mines dropped from special safety review get a closer look

Joseph Main, who heads MSHA, said the policies and mindset allowing those projects to escape earlier scrutiny have been abandoned under his watch.

"The career leadership at MSHA was following the existing policies in place prior to my arrival at MSHA, and I do not agree with these policies," Main said in a statement. In the future, Main added, enforcement decisions "will be based solely on what is best for the safety and health of the miners."

On Capitol Hill, some top Democrats say the OIG report is a clear indication Congress needs to evaluate MSHA's funding.

"Agency resources," Sen. Jay Rockefeller (D-W.Va.) said last week, "should not be a factor when MSHA determines whether or not to take enforcement action to protect miners from safety violations."