s 15 Duty to investigate
15.—(1) Subject to section 16, as soon as an immediately reportable matter has been notified to a nominated official under section 12(1), and if the Director believes that the circumstances of the reportable matter —(a) have, or are likely to have, significant implications for transport safety; and (b) may allow the TSIB to establish findings or make recommendations which may improve transport safety, an investigation must be carried out into the matter. (2) Subject to section 16, the Director —(a) may cause an investigation into any other transport occurrence notified to a nominated official under section 12(1) or (2); and (b) must cause an investigation into a transport occurrence (whether or not notified under section 12(1) or (2)) if ordered in writing by the Minister to do so. (3) To avoid doubt, the duty or power to investigate a transport occurrence under subsection (1) or (2) may extend to a transport occurrence that involves —(a) a combination of modes of transport vehicles; and (b) a combination of military and non‑military transport vehicles. (4) The Director may discontinue an investigation at any time except an investigation into a transport occurrence ordered by the Minister under subsection (2)(b).