The US Mine Safety and Health Administration said that the roof falls occurred on September 8-15. All were on working sections after the roof was bolted.

The MSHA did not identify the operations where the incidents occurred, but confirmed that three coal miners were injured.

“Such roof falls are particularly dangerous because they occur where most miners work,” investigators said.

“These types of accidents can be reduced, if not eliminated, when miners use…best practices as a guide.”

In addition to making frequent examinations of mine roof and being alert to changing conditions that can have an impact on the roof and rib, MSHA says mines must always follow their respective approved roof control plan.

When adverse conditions are found or anticipated, the agency reminded mines of the best practice procedure of installing additional support and using supplemental support methods for immediate roof control such as screen, steel straps, header boards and larger roof bolt plates.

When retreat mining, MSHA stressed, workers and equipment should be withdrawn immediately if a roof becomes unstable and, where appropriate, operators should use extra support in the vicinity of the last row of bolts to prevent a roof fall that can initiate in the unbolted cut and extend outby.

Finally, officials are reminding miners to use test holes for cracks and hazards above roof bolts and inform mine management of unusual conditions. Most importantly, no individual should ever travel under unsupported roof.