Mining firms are flagged for violations

Federal Mine Safety and Health Administration officials said they told 16 U.S. mining companies they have patterns of violating health and safety rules and warned them to clean up their acts or face heightened enforcement.

All but two of the companies operate coal mines or processing plants, the majority of them in Kentucky and West Virginia. This is the third time in the last year that the agency has singled out mines with patterns of serious violations.

Seven of eight operations notified last June reduced their serious violation rate by an average of 50% within months, according to the agency. The eighth closed.