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One worker has suffered multiple fractures, while another worker received neck and shoulder injuries, as a result of being struck by the falling material.
Both workers were treated at the scene and then transported to hospital.
The company suspended operations at the mine pending the outcome of the investigation, a Centennial spokesperson told Australia's Mining Monthly.
"Unfortunately two of our people - a father and son - working underground were injured," the spokesperson said.
"The injuries sustained are not believed to be life threatening and both persons were conveyed by helicopter to hospital at midday."
The Centennial spokesperson said the son was discharged from hospital on Wednesday evening and the father would be undergoing surgery for fractures to his femur.
The NSW Resources Regulator immediately deployed two inspectors to the mine and the incident scene remains under a non-disturbance notice.
"Our immediate priority is the safety and wellbeing of our people," the Centennial spokesperson said.
"An investigation into the incident is underway. As a result all relevant emergency services, industry and government departments were notified."
