Two miners have been killed after a roof collapsed in a Kentucky underground coal mine that has had a long history of safety violations.

The rock fall happened about four miles inside the Dotiki Mine, owned by Alliance Resource Partners, as the miners were using a continuous miner, a machine that digs coal for transport to the surface.

The US Mine Safety Health and Administration district supervisor Carl Boone said an investigation into the collapse will begin as soon as it is determined that the mine is safe to enter.

Federal inspectors cited the mine 840 times for safety violations and gave 40 closing orders over safety violations since January 2009.

In 2010 alone the mine received 214 citations with two closure orders.

The Mine Safety Health and Administration has cited the Dotiki Mine 17 times since January 2009 for failing to adequately secure roofs and walls against falling rock and coal, agency records show.

The accident happens as the MSHA considers toughening enforcement of safety rules following the deaths of 29 workers in an explosion at a West Virginia coal mine on 5 April.