The state's chief mine inspector has stopped work at Wollongong Coal's Wongawilli mine amid a major investigation into what the NSW Resources Regulator says are "significant safety issues".
The stop work order comes after the mining compliance regulator slapped the mine's operators with four separate prohibition notices last week.
NSW Resources Regulator inspectors visited the mine on March 13, to assess the adequacy of risk controls in place following a series of reported roof falls.
"While at the mine, inspectors also identified several safety issues with the mine's conveyor system; mine travel roads and production methods, which resulted in a total of three [prohibition] notices being issued," a regulator spokesman said.
"The mine reported another roof fall on the night of March 13. After a review of the fall, a further [prohibition] notice was placed on the mine."
The spokesman said resources regulator inspectors have taken compliance action in response to fire risks on conveyors on 13 separate occasions since August 2017.
"Of further concern, the mine reported spontaneous combustion in an accumulation of combustible material under a conveyor on the surface of the mine on February 19," he said.
"Following a review of all the concerns, the chief inspector made the decision to issue a stop work order."
The work order directs the mine operator to address issues relating to strata control and rectification works, which need to be undertaken on the mine conveyor system, the spokesman said.
The mine has 28 days to comply with the directions in the order.
"As the above matters are now subject of an investigation by the regulator's major investigation unit, further comment can not be provided," the spokesman said.
The Mercury sought comment from Wollongong Coal.
Last month, work at the mine was halted when a regulator-led probe found it didn't have a nominated manager of mechanical engineering, as required by workplace health and safety laws.
That issue was rectified.