Federal inspectors issued 163 citations and five orders at U.S. mine operations in December.
The Mine Safety and Health Administration says the inspections were conducted at 10 coal mines and seven other mines in 13 states.
The impact inspections began in 2010 after the Upper Big Branch mine explosion in West Virginia killed 29 coal miners. Since April 2010, MSHA has issued 15,695 citations and 1,299 orders.
Mines targeted by the inspections are those that have compliance concerns or poor compliance history.