After being loaded, the haul truck moved off from a dig face.

The area being mined was directly over underground workings.

As the truck drove over an underground intersection, the ground slumped underneath the rear left-hand side wheels.

The truck came to rest with its front two wheels off the ground.

The NSW Resources Regulator said the operator remained on the truck and was helped down with an elevated work platform.

"When procedural checks are the only method used to verify a control, this should be documented and recorded," it said.

"These records should be accessible to supervisors across shifts.

"Mine operators are reminded by the NSW Emergency Management Plan, via the Mine Sub Plan, are required to notify NSW Police as soon as they become aware a rescue is required."