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The method involves intentionally collapsing the roof of the mine to extract more coal.
Retreat mining has been a part of the mining process for generations and is considered standard practice in mines where reserves are running low.
The process involves unsettling support pillars of coal from inside the mine and letting the roof collapse as miners and equipment work their way out.
One of the workers who died was 46-year-old Gary Hensley, whose son told local media his father understood the risks.
"That's one of those things you always think about when you work in the mines," Caleb Hensley said.
Federal officials said the mine had so many safety problems it was deemed a "pattern violator", a rare designation reserved for the industry's worst offenders, only one step before the mine is forcibly closed.
Brody No. 1 is owned by a subsidiary of Patriot Coal, which in its annual report blamed the problems on a previous owner and said it was "vigorously contesting" the title.
