The Department of Labour usually opts for the more informal Investigation into workplace incidents. The reason is that they lack experienced inspectors who are ill equipped to conduct a Formal Inquiry where evidence is given under oath or affirmation and recorded. The Law of Privilege also applies like in criminal trials.
OHS Act section 31. Investigations.
(1) An inspector may investigate the circumstances of any incident which has occurred at or originated from a workplace or in connection with the use of plant or machinery which has resulted, or in the opinion of the inspector could have resulted, in the injury, illness or death of any person in order to determine whether it is necessary to hold a formal investigation in terms of section 32 .
(2) After completing the investigation in terms of subsection (1) the inspector shall submit a written report thereon, together with all relevant statements, documents and information gathered by him, to the attorney-general within whose area of jurisdiction such incident occurred and he shall at the same time submit a copy of the report, statements and documents to the chief inspector.
(3) Upon receipt of a report referred to in subsection (2), the attorney-general shall deal therewith in accordance with the provisions of the Inquests Act, 1959 (Act No. 58 of 1959), or the Criminal Procedure Act , 1977 (Act No. 51 of 1977), as the case may be.
(4) An inspector holding an investigation shall not incur any civil liability by virtue of anything contained in the report referred to in subsection (2).