For me, the following scenario is not so much about 'fire investigation by forum post' but in understanding what is meant by 'area of fire origin'.

The building was a large dormitory block. It was constructed primarily of timber with a metal sheeting roof and located in a rural area.

Post-fire, the building was a black hole.

Broken pieces from the building such as window glass and timber were located out to about 50 meters on 2 sides. A mostly intact glass window in a timber frame was on the ground closer to building.

A number of fire debris samples were found to contain 'medium petroleum distillates', the presence of which can not be explained.

A CCTV camera from over 1km away late at night showed a sudden glow from the direction of the building that seemed to expand beyond the perimeter of the walls and then reduce in size to the approximate perimeter of the building and progress from there.

The scene examination report is indicating that due to the degree of destruction, an area of fire origin can not be determined and therefore the cause must be listed as undetermined.

I know that NFPA says that with few exceptions, an area of origin is needed before continuing on to try and determine a cause.

Do we have a fire here that needs an 'area of origin' to progress to a cause determination?
Can the entire building be a legitimate 'area of origin'?
What would be your advice to the scene examiner (or the person tasked with reviewing their file)?

Thanks
Russell Mosely