Section 2(5)(a) in The Statutory Investigation Into Railway Accidents Rules, 1998
(a)If, for any reason, the concerned Commissioner of Railway Safety is unable to hold an inquiry at an early date after the occurrence of such an accident, he shall intimate by the fastest means of communication without any delay to the Chief Commissioner of Railway Safety of the reasons why the inquiry cannot be held by him. The Chief Commissioner may choose to conduct the inquiry himself or direct any other Commissioner to take up the inquiry or decide to let the inquiry be conducted by the Railway Administration. The concerned Commissioner shall thereafter notify the Railway Administration and the Railway Board accordingly.