Serious incidents do take days or weeks to investigate fully. The initial investigation will be focused on preserving information and getting the basic facts.  There will be a lot more to do later to complete a full investigation.

Arun

There can be valid reasons why a prompt report is required in a very tight timescale.

A skilful writer simply qualifies very very clearly limitations of the report due to limited time, and indicates further research needed.

Gathering of evidence and witness statements photographs and the like should be as soon as possible is that what the 48hrs is in reference to. If so then yes that is acceptable but as all have stated the complete investigate and outcome could take years if it’s complex.

From my experience low level takes up to a week to close all issues and further questions. medium 3-6 months complex a year to final close.

Who is imposing this timescale and why?

Forty eight hours to record and initiate an investigation process is ok (a bit slow in fact but taking into accounts weekends etc it makes sense) bit to expect a complete closed investigation in 48 hours is very arbitrary. Is it because they just want it closed off and are happy with some sort of headline root cause like “human failure” rather than getting into\the real nitty gritty which is usually some sort of management failure.

Part of the problem is that the term "investigation" means different things to different people.  It is much better to split the process into two stages:

1. The initial investigation, which is mostly concerned with gathering evidence and developing the timeline of events occurring at the time, and just before the incident.  This can and should be completed quite quickly. 

2. Analysis, which is where the real reason for the incident is established.  This can take a very long time.

This is alluded to in HSG 245, but I wish it were more explicit.

You may find this useful http://simplesensiblesaf...ion-recording-reporting/