In response to a series of recent reported roof falls, resources regulator inspectors attended the mine last week to review the risk controls in place to protect workers from roof failure.
During the investigation, inspectors identified significant safety issues on underground conveyor equipment, relating to fire risk.
"As a result, the mine operator was directed to shut the conveyors down until corrective actions are completed," the regulator said.
"Inspectors remain on site and investigations are ongoing due to concerns over the adequacy of the design and installation of strata support and the condition of underground travel roads, which has been the subject of previous compliance action."
The regulator said it was anticipated further significant compliance action could be taken subject to the outcomes of its investigations.
In February a section 195 notice was issued to Wongawilli prohibiting all mining activity and persons remaining underground, other than a minimal number to undertake maintenance activities due to the lack of a nominated manager of mechanical engineering.
That notice came after an investigation by the NSW Resources Regulator inspectors, which identified the mine did not have the nominated manager of mechanical engineering required by workplace health and safety laws.
The inspection also identified several hazards, which supported a view that the mine lacked appropriate mechanical supervision.