State inspectors delivered six charges for failing to comply with “approved roof control plan[s]” and one charge of deficient training to Stillhouse Mining, according to the Associated Press. Stillhouse is a division of Black Mountain Resources.

The inspectors’ citations come after an investigation by the Kentucky Department of Mine Safety and Licensing of the two August 3 roof falls that took the lives of Brandon Wilder, 23, and mine foreman Russell Cole, 39.

Both workers were performing the process of retreat mining, where coal pillars holding up roof are removed from exhausted sections of the mine. While such operations account for 10% of US production, operations’ life spans are typically less than longwall mining and are inherently more dangerous.

Approximately one-quarter of all underground deaths occur while workers are retreat mining. About 17 deaths over the last decade can be attributed to it, according to a local news report.

About 118 of Kentucky’s 252 underground coal facilities have retreat mining operations. Between July 2004 and August 2005, 4 miners were killed performing retreat mining in the state.

Stillhouse Mining has been in production since 1999 and employs 73 workers.