The US Department of Labor‘s Mine Safety and Health Administration (MSHA) has given closure orders to six underground coal mines in Kentucky following an inspection blitz last month.

The agency earlier initiated inspections at 57 coal mines with a history of underground violations that could lead to explosions.

Six mines, run by D&C Mining, Left Fork Mining, Manalapan Mining, Conshor Mining, Red Bird Coal and Cawood Enterprises, have received closure orders for violation of safety regulations including ventilation or combustible materials, the MSHA said.

The US Labor Department filed a suit against Manalapan and Left Fork for illegally providing advance notice of a federal inspector’s presence on mine properties.

The six mines during the inspection received 235 citations, 55 orders and one safeguard notice.

The inspection came weeks after one of the worst US coal mining disaster killed.

An explosion at Massey Energy’s Upper Big Branch operation in West Virginia killed 29 miners.