The NSW Resources Regulator said the fall occurred as workers were in the crib room preparing to start work in the area where the fall occurred.

The fall was the full width of the roadway and extended 15m to 20m.

"Monitoring in the intersection showed 31mm total displacement leading up to the fall," the regulator said.

"Initial investigations suggest it is a stress-related roof fall."

The regulator said underground mine operators should review the adequacy of their strata monitoring arrangements and associated trigger action response plans to ensure that workers are not exposed to unacceptable risks associated with strata failure.

"Mine operators should ensure that any abnormal changes in the strata behaviour are considered as potential indicators of geological change and respond appropriately," it said.

"Mine operators should ensure that the strata monitoring plan includes the timing for installation of strata monitoring devices and required installation of the devices in all high-risk areas including intersections."